JavaScript 实现数组的foreach

Array.prototype.forEach = function (action) {
for (var i = 0; i < this.length; i++) {
action(this[i]);
}
};
/**
* 以jqery 对象的方式迭代对象
* @param {} action
* @returns {}
*/
Array.prototype.forEachJq = function (action) {
for (var i = 0; i < this.length; i++) {
action($(this[i]));
}
};

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// Production steps of ECMA-262, Edition 5, 15.4.4.18

// Reference: http://es5.github.io/#x15.4.4.18

if (!Array.prototype.forEach) {

  Array.prototype.forEach = function(callback, thisArg) {

    var T, 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 (arguments.length > 1) {

      T = thisArg;

    }

    // 6. Let k be 0

    k = 0;

    // 7. Repeat, while k < len

    while (k < len) {

      var kValue;

      // 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. Call the Call internal method of callback with T as

        // the this value and argument list containing kValue, k, and O.

        callback.call(T, kValue, k, O);

      }

      // d. Increase k by 1.

      k++;

    }

    // 8. return undefined

  };

}