MDN上的標準Polyfill
if (!Function.prototype.bind) {
Function.prototype.bind = function(oThis) {
if (typeof this !== 'function') {
throw new TypeError('Function.prototype.bind - what is trying to be bound is not callable');
}
var aArgs = Array.prototype.slice.call(arguments, 1),
fToBind = this,
fNOP = function() {},
fBound = function() {
// this instanceof fBound === true時,說明返回的fBound被當做new的構造函數調用
return fToBind.apply(this instanceof fBound
? this
: oThis,
// 獲取調用時(fBound)的傳參.bind 返回的函數入參往往是這么傳遞的
aArgs.concat(Array.prototype.slice.call(arguments)));
};
// 維護原型關系
if (this.prototype) {
// Function.prototype doesn't have a prototype property
fNOP.prototype = this.prototype;
}
// 下行的代碼使fBound.prototype是fNOP的實例,因此
// 返回的fBound若作為new的構造函數,new生成的新對象作為this傳入fBound,新對象的__proto__就是fNOP的實例
fBound.prototype = new fNOP();
return fBound;
};
}
