implement myCall, myApply, myBind

Show the code directly.

myCall:

Function.prototype.myCall = function(ctx) {
    ctx = ctx || window;
    ctx.fn = this;
    let args = [...arguments].slice(1);
    let result = ctx.fn(...args);
    delete ctx.fn;
    return result;
}

myApply:

Function.prototype.myApply = function(ctx) {
    ctx = ctx || window;
    ctx.fn = this;
    let args = arguments[1];
    let result = ctx.fn(...args);
    delete ctx.fn;
    return result;
}

myBind:

Function.prototype.myBind = function(ctx) {
    let that = this;
    let args = [...arguments].slice(1);
    return function() {//currying
        const newArgs = [...arguments];
        return that.apply(ctx, args.concat(newArgs));
    }
}