JS interview question: FN call. call. call. Call (FN2) parsing

There is such a JS Interview questions , ask fn.call.call.call.call(fn2) What is the result ？

First say call Internal principle of function ：

1. You can change the value of the function this;
2. Execute function

Let's simulate Native call function ：

Function.prototype.call = function(context, ...args){
    
	context = context? Object(context) : window;
	//  change  this 
	context.fn = this;
	//  Execute function 
	return  context.fn(...args);
}

as follows ：

function fn(){
    
	console.log(11)
}

function fn2(){
    
	console.log(22)
}
 ask ：
fn.call.call.call.call(fn2)  What is the result ？

analysis ：

1. The front string fn.call.call.call.call No call , Just get the of the object call attribute , therefore , The result of this string is Function.call attribute .
2. So that string Namely Function.call.call(fn2); It can also be cleaved into fn3.call(fn2).
3. according to call Principle （ Please refer to the above call simulation ）, stay fn3 perform call, It is actually implemented in this way fn2.fn3().
4. because fn3 It's actually call function , therefore , fn2.fn3() Equivalent to fn2.call().
5. therefore , The final result of the above string of code , It's called fn2, So the result output 22.