Simple implementation
Function.prototype.bind = function(ctx,...res){
const self = this;
return function (...res2){
self.apply(ctx,res.concat(res2))
}
}
const fn = function(num){
console.log(this.name+''+num)
}
fn(1)
fn.bind({name:'luen'})(1)
Official implementation, in order to deal with the case of using new to create objects
//官方实现
if (!Function.prototype.bind) {
Function.prototype.bind = function (oThis) {
if (typeof this !== "function") {
// closest thing possible to the ECMAScript 5 internal IsCallable 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 () {
return fToBind.apply(this instanceof fNOP && oThis
? this
: oThis || window,
aArgs.concat(Array.prototype.slice.call(arguments)));
};
fNOP.prototype = this.prototype;
fBound.prototype = new fNOP();
return fBound;
};
}