实现一个bind

简易版

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Function.prototype.myBind = function (obj, ...args) {
  return (...rest) => this.call(obj, ...args, ...rest);
};

使用示例

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function f(arg) {
  console.log(this.a, arg);
}

// output: 3, 4
f.bind({ a: 3 })(4);

// output: 3, 4
f.myBind({ a: 3 })(4);

《JavaScript 权威指南》实现 bind

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if (!Function.prototype.bind) {
  Function.prototype.bind = function(o /*, args */) {
    var self = this, boundArgs = arguments;
    return function () {
      var i, args = [];
      for (i = 1; i < boundArgs.length; i++) {
        args.push(boundArgs[i])
      }
      for (i = 0; i < arguments.length; i++) {
        args.push(arguments[i])
     }
     return self.apply(o, args)
    }
  }
}