Javascript OOP 回调 "this"应用

Question

在我自己的 EACH 函数上创建 callback 时遇到问题。

我正在使用 OOP 方法来完成它。

基本上，我创建了自己的模仿 JQUERY 习惯的 javascript 库。

检查这个 fiddle 的 Action :https://jsfiddle.net/6pk068ep/1/

<div class="parent">
    <p class="child">child</p>
</div>
<div class="parent">
    <p class="child">child</p>
</div>

JavaScript:

"use strict";

(function(window) {

    var i, $, $Obj, ele; // global variable

    $ = function(el, length) {
        return new $Obj(el, length); // create new object
    };

    $Obj = function(el, length) {

      ele = document.querySelectorAll(el); // get selector element 

        this.length = ele.length; // count the length of ele

        for (i = 0; i < this.length; i++) {
            this[i] = ele[i]; // loop it
        }

    };

    $Obj.prototype = { // object prototype

       each : function(fn) { // create method each just like jquery

       var arr = []; // create array to store value

       for (i = 0; i < this.length; i++) {          
         arr.push(this[i]); // push it to arr variable
         }

       fn.apply(this, arr); // IS THIS THE CORRECT WAY TO APPLY IT? 
       return this; // return this, so, it's chainable for other method

      }

    };

window.$ = $; // make dollar sign global object

})(window);

$(".child").each(function() {

    console.log(this);
    this.style.color = "red"; // not working, what's wrong with my code? is it because my "apply" wrong?

});

如何将那些 .child 风格的颜色变成红色？

我的代码有什么问题？

提前致谢...

Answer 1

当您说 each() 时，假设将为集合中的每个项目调用回调，因此在这种情况下您需要在 for 循环中调用回调。

另请注意，ele 和 i 等变量不是全局变量，它们应该是您使用它们的函数的局部变量。

"use strict";

(function(window) {

  var $, $Obj; // global variable

  $ = function(el, length) {
    return new $Obj(el, length); // create new object
  };

  $Obj = function(el, length) {
    var ele, i;

    ele = document.querySelectorAll(el); // get selector element 

    this.length = ele.length; // count the length of ele

    for (i = 0; i < this.length; i++) {
      this[i] = ele[i]; // loop it
    }

  };

  $Obj.prototype = { // object prototype

    each: function(fn) { // create method each just like jquery
      var i;

      for (i = 0; i < this.length; i++) {
        fn.call(this[i], this[i], i);
      }

      return this; // return this, so, it's chainable for other method

    }

  };

  window.$ = $; // make dollar sign global object

})(window);

$(".child").each(function() {

  console.log(this);
  this.style.color = "red"; // not working, what's wrong with my code? is it because my "apply" wrong?

});

<div class="parent">
  <p class="child">child</p>
</div>
<div class="parent">
  <p class="child">child</p>
</div>