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前端知识复习 code snippet ​

array.prototype.every 标准

  1. Let O be ? ToObject(this value).
  2. Let len be ? LengthOfArrayLike(O).
  3. If IsCallable(callbackfn) is false, throw a TypeError exception.
  4. Let k be 0.
  5. Repeat, while k < len,
    • Let Pk be ! ToString(k).
    • Let kPresent be ? HasProperty(O, Pk).
    • If kPresent is true, then
      • Let kValue be ? Get(O, Pk).
      • Let testResult be ! ToBoolean(? Call(callbackfn, thisArg, « kValue, k, O »)).
      • If testResult is true, return false.
  • Set k to k + 1.
  1. Return true.

代码 ​

javascript
Array.prototype.myEvery = function (callbackfn, thisArg) {
    if (this == undefined) {
        throw TypeError('Cannot read property filter of ' + this);
    }
    if (typeof callbackfn !== 'function') {
        throw TypeError(callbackfn + ' is not a function');
    }

    var O = Object(this);
    var len = O.length >>> 0;
    for (var k = 0; k < len; k++) {
        if (k in O) {
            var kValue = O[k];
            if (!callbackfn.call(thisArg, kValue, k, O)) return false;
        }
    }
    return true;
};