手写Array.prototype.every

May 24, 2020

前端知识复习 code snippet

Let O be ? ToObject(this value).

Let len be ? LengthOfArrayLike(O).

If IsCallable(callbackfn) is false, throw a TypeError exception.

Let k be 0.

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.

Return true.

代码

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;
};