js的apply、call、bind

javascript的apply、call、bind实现

Function.prototype.myCall=function(context,...arg){
    let ctx=context||window
    let uuid= Symbol()

    ctx[uuid]=this

    let result=ctx[uuid](...arg)

    return result

}
Function.prototype.myApply=function(context,arg){
    let ctx=context||window
    let uuid= Symbol()

    ctx[uuid]=this

    let result=ctx[uuid](...arg)

    delete ctx[uuid]

    return result
    
}
Function.prototype.myBind=function(context,arg){
    const fn =this
    return function(...innerArgs){
        return fn.apply(context,arg.concat(innerArgs))
    }
}
const obj={
	name:'jack'
}
function greet(args){
	console.log('xx',this,args)
}

greet()
greet.apply(obj,['apply rose'])
greet.call(obj,'call rose')
let f=greet.bind(obj)
f('bind')

输出

“xx” [object Window] undefined
“xx” Object { name: “jack” } “apply rose”
“xx” Object { name: “jack” } “call rose”
“xx” Object { name: “jack” } “bind”