function fn(a,b,c){
console.log(a)
console.log(b)
console.log(c)
}
Function.prototype._bind = function(context,...bindArgs){
let fn = this.name;
context[fn] = this; //fn函数
return (...arg) => context.fn(...bindArgs,...arg);//根据bind规则将bind参数传入fn函数中
}
var test = fn._bind(this,1)
test(2,3) //1 2 3