CODEWITHSUNDEEP
javascript
Dominik Gabor
Dominik Gabor

Reputation: 31

Function().prototype.call() implementation

I´m trying to understand how Function.prototype.call() works. I know what it does, and I can work with it, but I´m curious about how this method is implemented.

Is it possible to write a javascript-method from scratch that does exactly the same?

Upvotes: 2

Views: 1095

Answers (1)

georg
georg

Reputation: 214959

It's not possible to "unwrap" variable arguments without eval. If it's fine with you, you can try this:

function myCall(fun, obj) {
    var args = [].slice.call(arguments, 2);
    var arglist = args.map(function(_, n) { return "args[" + n + "]" }).join(',');
    obj._tmp = fun;
    return eval("obj._tmp(" + arglist + ")")
}

Example:

foo = {
    x: 123
}

bar = function(y) { return this.x + y }

console.log(myCall(bar, foo, 444))

Upvotes: 2

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