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Using currying function to implement bind method in javascript

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Release： 2018-09-28 13:27:25

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• Ke Lihua’s function idea: a js pre-processing idea; using the principle of function execution to form a non-destructible scope, all content that needs to be pre-processed is stored in this non-destructible scope. And returns a small function. From now on, we will execute small functions. In the small function, we can perform relevant operations on the previously stored values;

• The currying function mainly plays a preprocessing role Function;

• The function of bind method: pre-process this in the callback method passed in as context context;

/**
* bind方法实现原理1
* @param callback [Function] 回调函数
* @param context [Object] 上下文
* @returns {Function} 改变this指向的函数
*/
function bind(callback,context) {
  var outerArg = Array.prototype.slice.call(arguments,2);// 表示取当前作用域中传的参数中除了fn,context以外后面的参数；
  return function (){
    var innerArg = Array.prototype.slice.call(arguments,0);//表示取当前作用域中所有的arguments参数；
    callback.apply(context,outerArg.concat(innerArg));
  }
}

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/**
* 模仿在原型链上的bind实现原理(柯理化函数思想)
* @param context [Object] 上下文
* @returns {Function} 改变this指向的函数
*/
Function.prototype.mybind = function mybind (context) {
  var _this = this;
  var outArg = Array.prototype.slice.call(arguments,1);
  // 兼容情况下
  if(&#39;bind&#39; in Function.prototype) {
    return this.bind.apply(this,[context].concat(outArg));
  }
  // 不兼容情况下
  return function () {
    var inArg = Array.prototype.slice.call(arguments,0);
    inArg.length === 0?inArg[inArg.length]=window.event:null;
    var arg = outArg.concat(inArg);
    _this.apply(context,arg);
  }
}

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