让forEach兼容IE8

Posted 2020-09-24 锅盖er

今天在做项目中遇到一个问题，就是forEach 不兼容IE8；后经查阅资料完美解决问题。

资料：https://developer.mozilla.org/en-US/docs/Web/javascript/Reference/Global_Objects/Array/forEach?v=example

 1 //官网查询的兼容代码段
 2 // Production steps of ECMA-262, Edition 5, 15.4.4.18
 3 // Reference: http://es5.github.io/#x15.4.4.18
 4 if (!Array.prototype.forEach) {
 5 
 6   Array.prototype.forEach = function(callback/*, thisArg*/) {
 7 
 8     var T, k;
 9 
10     if (this == null) {
11       throw new TypeError(‘this is null or not defined‘);
12     }
13 
14     // 1. Let O be the result of calling toObject() passing the
15     // |this| value as the argument.
16     var O = Object(this);
17 
18     // 2. Let lenValue be the result of calling the Get() internal
19     // method of O with the argument "length".
20     // 3. Let len be toUint32(lenValue).
21     var len = O.length >>> 0;
22 
23     // 4. If isCallable(callback) is false, throw a TypeError exception. 
24     // See: http://es5.github.com/#x9.11
25     if (typeof callback !== ‘function‘) {
26       throw new TypeError(callback + ‘ is not a function‘);
27     }
28 
29     // 5. If thisArg was supplied, let T be thisArg; else let
30     // T be undefined.
31     if (arguments.length > 1) {
32       T = arguments[1];
33     }
34 
35     // 6. Let k be 0.
36     k = 0;
37 
38     // 7. Repeat while k < len.
39     while (k < len) {
40 
41       var kValue;
42 
43       // a. Let Pk be ToString(k).
44       //    This is implicit for LHS operands of the in operator.
45       // b. Let kPresent be the result of calling the HasProperty
46       //    internal method of O with argument Pk.
47       //    This step can be combined with c.
48       // c. If kPresent is true, then
49       if (k in O) {
50 
51         // i. Let kValue be the result of calling the Get internal
52         // method of O with argument Pk.
53         kValue = O[k];
54 
55         // ii. Call the Call internal method of callback with T as
56         // the this value and argument list containing kValue, k, and O.
57         callback.call(T, kValue, k, O);
58       }
59       // d. Increase k by 1.
60       k++;
61     }
62     // 8. return undefined.
63   };
64 }
65 //此处放兼容代码
66 /*兼容代码*/
67 //resultArr数组
68 resultArr.forEach(function (iterm, index) {
69       //内容                 
70 })