javascript – array.map功能不支持IE8标准？

我没有IE8,所以我正在IE10内测试IE8.当我切换到文档模式的“IE8标准”时,数组对象的 JavaScript地图函数给出了一个javascript错误：对象不支持属性或方法’map’

但是当我切换到文档模式的“标准”时,没有错误.我应该测试哪种模式？

如果IE8不支持map功能,有没有办法模拟？

解决方法

不支持,但 MDN提供了非常接近规格的垫片：

// Production steps of ECMA-262,Edition 5,15.4.4.19
// Reference: http://es5.github.com/#x15.4.4.19
if (!array.prototype.map) {
  array.prototype.map = function(callback,thisArg) {

    var T,A,k;

    if (this == null) {
      throw new TypeError(" this is null or not defined");
    }

    // 1. Let O be the result of calling ToObject passing the |this| value as the argument.
    var O = Object(this);

    // 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
    // 3. Let len be ToUint32(lenValue).
    var len = O.length >>> 0;

    // 4. If IsCallable(callback) is false,throw a TypeError exception.
    // See: http://es5.github.com/#x9.11
    if (typeof callback !== "function") {
      throw new TypeError(callback + " is not a function");
    }

    // 5. If thisArg was supplied,let T be thisArg; else let T be undefined.
    if (thisArg) {
      T = thisArg;
    }

    // 6. Let A be a new array created as if by the expression new Array(len) where Array is
    // the standard built-in constructor with that name and len is the value of len.
    A = new Array(len);

    // 7. Let k be 0
    k = 0;

    // 8. Repeat,while k < len
    while(k < len) {

      var kValue,mappedValue;

      // a. Let Pk be ToString(k).
      //   This is implicit for LHS operands of the in operator
      // b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
      //   This step can be combined with c
      // c. If kPresent is true,then
      if (k in O) {

        // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
        kValue = O[ k ];

        // ii. Let mappedValue be the result of calling the Call internal method of callback
        // with T as the this value and argument list containing kValue,k,and O.
        mappedValue = callback.call(T,kValue,O);

        // iii. Call the DefineOwnProperty internal method of A with arguments
        // Pk,Property Descriptor {Value: mappedValue,: true,Enumerable: true,Configurable: true},// and false.

        // In browsers that support Object.defineProperty,use the following:
        // Object.defineProperty(A,Pk,{ value: mappedValue,writable: true,enumerable: true,configurable: true });

        // For best browser support,use the following:
        A[ k ] = mappedValue;
      }
      // d. Increase k by 1.
      k++;
    }

    // 9. return A
    return A;
  };      
}

原文地址：https://www.jb51.cc/js/155428.html