js数组方法forEach,map,filter,every,some实现-白红宇

js数组方法forEach,map,filter,every,some实现

阅读量：4549 次

发布时间：2019-06-08

本文共 2946 字，大约阅读时间需要 9 分钟。

Array.prototype.map = function(fun /*, thisp*/){  var len = this.length;  if (typeof fun != "function")    throw new TypeError();  var res = new Array(len);  var thisp = arguments[1];  for (var i = 0; i < len; i++)  {    if (i in this)      res[i] = fun.call(thisp, this[i], i, this);  }  return res;};Array.prototype.filter = function(fun /*, thisp*/){  var len = this.length;  if (typeof fun != "function")    throw new TypeError();  var res = new Array();  var thisp = arguments[1];  for (var i = 0; i < len; i++)  {    if (i in this)    {      var val = this[i]; // in case fun mutates this      if (fun.call(thisp, val, i, this))        res.push(val);    }  }  return res;};Array.prototype.some = function(fun /*, thisp*/){  var len = this.length;  if (typeof fun != "function")    throw new TypeError();  var thisp = arguments[1];  for (var i = 0; i < len; i++)  {    if (i in this && fun.call(thisp, this[i], i, this))      return true;  }  return false;};Array.prototype.every = function(fun /*, thisp*/){  var len = this.length;  if (typeof fun != "function")    throw new TypeError();  var thisp = arguments[1];  for (var i = 0; i < len; i++)  {    if (i in this && !fun.call(thisp, this[i], i, this))    return false;  }  return true;};Array.prototype.forEach = function(fun /*, thisp*/){  var len = this.length;  if (typeof fun != "function")    throw new TypeError();  var thisp = arguments[1];  for (var i = 0; i < len; i++)  {    if (i in this)      fun.call(thisp, this[i], i, this);  }};

Array.prototype.map = function(fun /*, thisp*/) {

var len = this.length; if (typeof fun != "function") thrownewTypeError(); var res = newArray(len); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i inthis) res[i] = fun.call(thisp, this[i], i, this); } return res; }; Array.prototype.filter = function(fun /*, thisp*/) {

var len = this.length; if (typeof fun != "function") thrownewTypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i inthis && fun.call(thisp, this[i], i, this)) returntrue; } returnfalse; }; Array.prototype.every = function(fun /*, thisp*/) {

var len = this.length; if (typeof fun != "function") thrownewTypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i inthis && !fun.call(thisp, this[i], i, this)) returnfalse; } returntrue; }; Array.prototype.forEach = function(fun /*, thisp*/) {

var len = this.length; if (typeof fun != "function") thrownewTypeError(); var thisp = arguments[1]; for (var i = 0; i < len; i++) { if (i inthis) fun.call(thisp, this[i], i, this); } };

转载于:https://www.cnblogs.com/wayofeng/p/7273960.html

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