Summary of methods for traversing arrays in JavaScript-JS Tutorial-php.cn

Summary of methods for traversing arrays in JavaScript

黄舟

Release： 2017-11-09 14:59:15

Original

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I believe everyone knows the role of arrays. It manages the storage space of multiple data in batches. Arrays have a long data structure, which can greatly improve the execution efficiency of programs, whether in PHP or ## In #JavaScript or in jQuery, the form of arrays is divided into index arrays and associative arrays, so how to traverse the array! Below we will give you a detailed introduction toJavaScript arrayTraversal~

1.for(){}Traversing the array

<script type="text/javascript">
 <!--
var arr = new Array(13.5,3,4,5,6);
for(var i=0;i<arr.length;i++){
 arr[i] = arr[i]/2.0;
}
alert(arr);
 //-->
 </script>

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2.for in loop traverses the array

<html>
<body>
<script type="text/javascript">
var x
var mycars = new Array()
mycars[0] = "Saab"
mycars[1] = "Volvo"
mycars[2] = "BMW"
for (x in mycars)
{
document.write(mycars[x] + "<br />")
}
</script>
</body>
</html>

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3.forEach methodNote: the forEach() method is introduced by the ES5.1 standard.

var arr=[1,2,3,4,5,6];
arr.forEach(function(v,i){//v==value　为arr项，i==index　为arr索引
    console.log(i+&#39;  &#39;v );
})//输出0  11  22  33  44  55  6

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4. A new method has been added in the latest ES6 standard==for of==

for of method　 You can use subscript loops when traversing Array, but you cannot use subscripts when traversing Map and Set. Map, set – no subscript, cannot use index to traverse
In order to unify collection types, the ES6 standard introduces a new iterable type,
Array, Map and Set all belong to iterable types.
==Collections with iterable types can be traversed through the new for ... of loop. ==

var arr=[1,2,3,4,5,6];for(var value of Arr){
    console.log(value);
}  //输出123456

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Summary:

The JavaScript method of traversing arrays has been summarized. Do you believe that you are familiar with arrays? We have a certain understanding of traversal , but in our actual development, we still need to choose according to our own needs, because the execution efficiency of some methods is not the best! So use with caution!

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