8 basic knowledge of JS that you must pay attention to-JS Tutorial-php.cn

8 basic knowledge of JS that you must pay attention to

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Release： 2018-03-13 13:16:11

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This time I will bring you 8 basic knowledge of JS that must be paid attention to. 8 basic knowledge of JS that must be paid attention to. What are the precautions?. Here are the actual cases. Let’s take a look. one time.

1 Modify the class name of the element in JS: You can modify it through className, but you cannot use class

       function toRed() {            var tobox = document.getElementById(&#39;box1&#39;);
            tobox.className = &#39;tmpBox&#39;;
        }

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2 Function parameter passing

<html lang="en"><head>
    <meta charset="UTF-8">
    <title>02-函数传参数</title>
    <style>
        #div1{width: 200px; height: 200px; border: 1px  solid #000;}    </style>
    <script>
        function setColor(color) {            var oDiv = document.getElementById(&#39;div1&#39;);
            oDiv.style.backgroundColor = color;
        }    </script></head><body><input type="button" value="变绿" onclick="setColor(&#39;green&#39;)"><input type="button" value="变黄" onclick="setColor(&#39;yellow&#39;)"><input type="button" value="变黑" onclick="setColor(&#39;black&#39;)"><div id="div1"></div></body></html>

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3 The second method of modifying attributes: (Use when the attribute to be modified is not fixed)

You can use oDiv. style[attribute name] = value; to dynamically modify attributes and values

//括号里放的是变量
       function setStyle(propertyName,value) { 
          var oDiv = document.getElementById(&#39;div1&#39;);
          oDiv.style[propertyName] = value;
      }

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<html lang="en"><head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        #div1{            width: 100px;height: 100px;border: 1px solid #000;background-color: skyblue;
        }    </style>
    <script>
        function setStyle(propertyName,value) {            var oDiv = document.getElementById(&#39;div1&#39;);
            oDiv.style[propertyName] = value;
        }    </script></head><body><input type="button" value="变高" onclick="setStyle(&#39;height&#39;,&#39;200px&#39;)"><input type="button" value="变宽" onclick="setStyle(&#39;width&#39;,&#39;200px&#39;)"><input type="button" value="变红" onclick="setStyle(&#39;background&#39;,&#39;red&#39;)"><div id="div1"></div></body></html>

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4. The difference between style and className

##Element.style.Attribute = xxx; is the modified interline (inline) style, and its priority is relatively high!!! For example: oDiv.style.backgroundColor = ' red';

className: You can find the corresponding style by specifying the class name;
But if you use style and then use className to specify the style, it will have no effect!!!!

Note: Either use style to set the style, or use className to specify the style alone. They cannot be mixed, and unknown errors will occur!

5.提取行间事件

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window.onload The

behavior will be executed only after the page is loaded. Separation of style and structure: JS CSS HTML separation

Extract events

Add events to elements

<html lang="en"><head>
    <meta charset="UTF-8">
    <title>05-提取行间事件</title>
    <script>
        //window.onload 页面加载完成时才执行
        window.onload = function () {            var oBtn = document.getElementById(&#39;btn1&#39;);            //给元素添加事件
            oBtn.onclick = function () {  //匿名函数
                alert(&#39;我是打酱油的&#39;);
            };
        }    </script></head><body><input id="btn1" type="button" value="按钮"></body></html>

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6.JS gets child elements from parent elements

Get the input from the code below

<div id="box1">
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br>
    <input type="checkbox"> <br></div>

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and put it down as follows:

window.onload =function (){   var oDiv = document.getElementById(&#39;box1&#39;); //现获取父元素div
   var inputs = oDiv.getElementsByTagName(&#39;input&#39;); //再通过div获取到里面所有的input}

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7. innerHTML

is used to set the container The content of the tag can be text or HTML (tag).

<html lang="en"><head>
    <meta charset="UTF-8">
    <title>08-innerHTML</title>
    <style>
        .content{            width: 200px;            height: 200px;            border: 1px solid #000;
        }    </style>
    <script>
        window.onload = function () {            var oText = document.getElementById(&#39;textField&#39;);            var oBtn = document.getElementById(&#39;button&#39;);            var oContent = document.getElementById(&#39;div-content&#39;);
            oBtn.onclick = function () {
                oContent.innerHTML = oText.value;//可以往里放文字,标签等
            }
        }    </script></head><body><input type="text" id="textField"><input type="button" value="点击" id="button"><div class="content" id="div-content"></div></body></html>

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8. String splicing:

var str = &#39;我叫小明&#39;+12+&#39;岁&#39;+168+&#39;2017&#39;; >>>  结果:我叫小明12岁1682017var num = &#39;9+6等于&#39;+(9+6); >>>  结果: 9 + 6 等于 15

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I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!