How to force a different pointer on a bonded function

I am confused about how bind and apply work.

bind

apply

I know bind binds a pointer to a function and apply tell the function to run with the pointer given at the call time, so I did a little test and used the apply pointer but it didn't have any effects, it still uses the bind pointer.

bind

apply

apply

bind

How can I force the function to use a different pointer without bind a permanent new pointer?

Here is my test:

expected output:
this.test is not a function

this.test

class A
test()

printA()
this.test();
console.log('A');



const dummy = function(func)
func.apply(this, );
;

const a = new A();
dummy(a.printA.bind(a));

1 Answer
1

The this bound to a function reference with .bind cannot be overridden by passing a different this to .apply.

this

.bind

this

.apply

Think of .bind as working like this (but ignoring the ability of the real version to also attach extra preset function parameters):

.bind

function bind(fn, ctx)
return function(...args)
return fn.apply(ctx, args);



let boundFunc = bind(myfunc, myctx);
boundFunc.apply(newctx, arg1, arg2);


You should be able to see that there's no way for newctx to be passed to myfunc via boundFunc because the innermost call to .apply in the closure inside bind() determines the passed context (i.e. the one supplied to bind).

newctx

myfunc

boundFunc

.apply

bind()

bind

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.