手写Array.prototype.some

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 true.

Set k to k + 1.

Return false.

代码

Array.prototype.mySome = 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 true;
        }
    }
    return false;
}