js loop traversal-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

js loop traversal

不言

Apr 26, 2018 pm 02:48 PM

javascript Traverse

The content of this article is about loop traversal in js. Now I share it with everyone, and it can also be used as a reference for friends in need

Method 1

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">i </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">0</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">;<span style="margin:0px;padding:0px;">i</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">.length;<span style="margin:0px;padding:0px;">i</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">++</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">){<br/>        </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">//...<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">    }</span>

Copy after login

# The disadvantage of method 1 using a for loop to traverse the array is that the code is not enough concise.

## The following is a more concise way of writing.

Method 2

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br/><span style="margin:0px;padding:0px;">    arr</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">forEach</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">function </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(253,151,31);">value</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(253,151,31);">index</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">) {<br/>       </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">//...<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">    });<br/>    <br/></span>

Copy after login

# This uses the Foreach loop code to be much less. The writing is more concise. The disadvantage is that the entire cycle cannot be stopped.

#Method 3

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">i </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">in </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">){<br/>        </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">//...<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">    }<br/>    <br/></span>

Copy after login

for...in循环更常用于对象的循环，如果用于数组的循环，那么就要注意了，上述代码中每次循环中得到的i是字符串类型，而不是预料中的数字类型，要想对它进行运算，那得先要进行类型转换，造成不方便。

来看看for...of的是实现：

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">value </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">of <span style="margin:0px;padding:0px;">arr</span>){<br/>        <span style="margin:0px;padding:0px;">console</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">log</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">value</span>);<br/>    }<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    //</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">打印结果：依次输出：</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">1 2 3 4 5<br/><br/></span>

Copy after login

看样子是不是有点眼熟，很像for...in？确实很像。它的实现跟for...in很类似。

我们列举一下for...of的优势：

写法比for循环简洁很多；
可以用break来终止整个循环，或者continute来跳出当前循环，继续后面的循环；
结合keys( )获取到循环的索引，并且是数字类型，而不是字符串类型。

分别来展示一下上述的几个优点：

循环可以终止

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">value </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">of <span style="margin:0px;padding:0px;">arr</span>){<br/>        </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">if</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">value </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">== </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">){<br/>            </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">//</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">终止整个循环<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">            break</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">;<br/>        }<br/>        <span style="margin:0px;padding:0px;">console</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">log</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">value</span>);<br/>    }<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    //</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">打印结果：</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">1 2<br/><br/></span>

Copy after login

以上案例：用break实现了终止整个循环，不会继续后面的遍历，所以打印结果为：1 2。

可跳过当前循环

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">value </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">of <span style="margin:0px;padding:0px;">arr</span>){<br/>        </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">if</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">value </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">== </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">){<br/>            </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">//</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">跳过当前循环，继续后面的循环<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">            continue</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">;<br/>        }<br/>        <span style="margin:0px;padding:0px;">console</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">log</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">value</span>);<br/>    }<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    //</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">打印结果：</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">1 2 4  5<br/><br/></span>

Copy after login

用continue跳过当前循环，继续后面的循环，所以打印结果为：1 2 4 5。

得到数字类型的索引

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    var </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">arr </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">[</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">1</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">2</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">3</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">4</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">,</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(174,129,255);">5</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">];<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">index </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">of <span style="margin:0px;padding:0px;">arr</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">keys</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">()){<br/>        <span style="margin:0px;padding:0px;">console</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">log</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">index</span>);<br/>    }<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    //</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">打印结果：依次输出</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">:0 1 2 3 4<br/><br/></span>

Copy after login

使用数组的扩展keys( )（第八节有介绍，点击查看），获取键名再遍历，得到的index是数字类型的。

此外，相比于for...in循环专门为对象设计，for...of循环的适用范围更广。

遍历字符串

for...of 支持字符串的遍历。

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);"><br/>    let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">word </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(230,219,116);">"</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(230,219,116);">我是前端小菜鸟</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(230,219,116);">"</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">;<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">w </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">of <span style="margin:0px;padding:0px;">word</span>){<br/>        <span style="margin:0px;padding:0px;">console</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">log</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">w</span>);<br/>    }<br/></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    //</span><span style="margin:0px;padding:0px;font-size:18px;color:rgb(117,113,94);">打印结果：我  是  前  端  小  菜  鸟<br/><br/></span>

Copy after login

遍历DOM List

for...of支持类数组的遍历，例如DOM List。

<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);"><br/>    <</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(227,227,255);">p</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">><span style="margin:0px;padding:0px;">1</span></</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(227,227,255);">p</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">><br>    <</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(227,227,255);">p</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">><span style="margin:0px;padding:0px;">2</span></</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(227,227,255);">p</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">><br>    <</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(227,227,255);">p</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">><span style="margin:0px;padding:0px;">3</span></</span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(227,227,255);">p</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">><br></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    //</span><span style="margin:0px;padding:0px;color:rgb(117,113,94);">假设有<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;">3</span>个<span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;">p</span>元素</span><span style="margin:0px;padding:0px;"><br></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">pList </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">= </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">document</span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">getElementsByTagName</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(230,219,116);">'p'</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">);<br><br></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">    for</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(249,38,114);">let </span><span style="margin:0px;padding:0px;"><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">p </span></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">of <span style="margin:0px;padding:0px;">pList</span>){<br>        <span style="margin:0px;padding:0px;">console</span>.</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(166,226,46);">log</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(248,248,242);">(<span style="margin:0px;padding:0px;">p</span>);<br></span><span style="margin:0px;padding:0px;color:rgb(248,248,242);font-family:Consolas;font-size:18px;line-height:1.6;">    }<br></span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);">    // </span><span style="margin:0px;padding:0px;color:rgb(117,113,94);">打印结果：</span><span style="margin:0px;padding:0px;font-size:18px;font-family:Consolas;color:rgb(117,113,94);"><p>1</p><br></span><span style="margin:0px;padding:0px;color:rgb(117,113,94);font-family:Consolas;font-size:18px;line-height:1.6;">    //          <p>2</p><br>    //          <p>3</p></span>

Copy after login

还有一些其它的遍历后续再添加~···

Hot AI Tools

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

R.E.P.O. Best Graphic Settings

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Assassin's Creed Shadows: Seashell Riddle Solution

2 weeks ago By DDD

R.E.P.O. How to Fix Audio if You Can't Hear Anyone

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

WWE 2K25: How To Unlock Everything In MyRise

1 months ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Zend Studio 13.0.1

Powerful PHP integrated development environment

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Where is the login entrance for gmail email?

7514

CakePHP Tutorial

1378

What is the format of the account name of steam

win11 activation key permanent

nyt connections hints and answers

Related knowledge

How to implement an online speech recognition system using WebSocket and JavaScript Dec 17, 2023 pm 02:54 PM

How to use WebSocket and JavaScript to implement an online speech recognition system Introduction: With the continuous development of technology, speech recognition technology has become an important part of the field of artificial intelligence. The online speech recognition system based on WebSocket and JavaScript has the characteristics of low latency, real-time and cross-platform, and has become a widely used solution. This article will introduce how to use WebSocket and JavaScript to implement an online speech recognition system.

WebSocket and JavaScript: key technologies for implementing real-time monitoring systems Dec 17, 2023 pm 05:30 PM

WebSocket and JavaScript: Key technologies for realizing real-time monitoring systems Introduction: With the rapid development of Internet technology, real-time monitoring systems have been widely used in various fields. One of the key technologies to achieve real-time monitoring is the combination of WebSocket and JavaScript. This article will introduce the application of WebSocket and JavaScript in real-time monitoring systems, give code examples, and explain their implementation principles in detail. 1. WebSocket technology

How to use JavaScript and WebSocket to implement a real-time online ordering system Dec 17, 2023 pm 12:09 PM

Introduction to how to use JavaScript and WebSocket to implement a real-time online ordering system: With the popularity of the Internet and the advancement of technology, more and more restaurants have begun to provide online ordering services. In order to implement a real-time online ordering system, we can use JavaScript and WebSocket technology. WebSocket is a full-duplex communication protocol based on the TCP protocol, which can realize real-time two-way communication between the client and the server. In the real-time online ordering system, when the user selects dishes and places an order

How to implement an online reservation system using WebSocket and JavaScript Dec 17, 2023 am 09:39 AM

How to use WebSocket and JavaScript to implement an online reservation system. In today's digital era, more and more businesses and services need to provide online reservation functions. It is crucial to implement an efficient and real-time online reservation system. This article will introduce how to use WebSocket and JavaScript to implement an online reservation system, and provide specific code examples. 1. What is WebSocket? WebSocket is a full-duplex method on a single TCP connection.

Java how to loop through a folder and get all file names Mar 29, 2024 pm 01:24 PM

Java is a popular programming language with powerful file handling capabilities. In Java, traversing a folder and getting all file names is a common operation, which can help us quickly locate and process files in a specific directory. This article will introduce how to implement a method of traversing a folder and getting all file names in Java, and provide specific code examples. 1. Use the recursive method to traverse the folder. We can use the recursive method to traverse the folder. The recursive method is a way of calling itself, which can effectively traverse the folder.

JavaScript and WebSocket: Building an efficient real-time weather forecasting system Dec 17, 2023 pm 05:13 PM

JavaScript and WebSocket: Building an efficient real-time weather forecast system Introduction: Today, the accuracy of weather forecasts is of great significance to daily life and decision-making. As technology develops, we can provide more accurate and reliable weather forecasts by obtaining weather data in real time. In this article, we will learn how to use JavaScript and WebSocket technology to build an efficient real-time weather forecast system. This article will demonstrate the implementation process through specific code examples. We

Simple JavaScript Tutorial: How to Get HTTP Status Code Jan 05, 2024 pm 06:08 PM

JavaScript tutorial: How to get HTTP status code, specific code examples are required. Preface: In web development, data interaction with the server is often involved. When communicating with the server, we often need to obtain the returned HTTP status code to determine whether the operation is successful, and perform corresponding processing based on different status codes. This article will teach you how to use JavaScript to obtain HTTP status codes and provide some practical code examples. Using XMLHttpRequest

How to get HTTP status code in JavaScript the easy way Jan 05, 2024 pm 01:37 PM

Introduction to the method of obtaining HTTP status code in JavaScript: In front-end development, we often need to deal with the interaction with the back-end interface, and HTTP status code is a very important part of it. Understanding and obtaining HTTP status codes helps us better handle the data returned by the interface. This article will introduce how to use JavaScript to obtain HTTP status codes and provide specific code examples. 1. What is HTTP status code? HTTP status code means that when the browser initiates a request to the server, the service

See all articles

js loop traversal

Hot AI Tools

Undresser.AI Undress

AI Clothes Remover

Undress AI Tool

Clothoff.io

AI Hentai Generator

Hot Article

Hot Tools

Notepad++7.3.1

SublimeText3 Chinese version

Zend Studio 13.0.1

Dreamweaver CS6

SublimeText3 Mac version

Hot Topics