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Suggestions for using `...arguments` while working with functions in javascript.

Gokul Kathirvel on April 06, 2018

In many situations, using arguments to pass the function args would lead to bugs as we totally unaware the actual args. When to use these such notations and when not to?

Meghan (she/her) • Apr 6 '18

First note, try not to use arguments as it was reserved in the past and not allowed in strict mode anymore.

Also are you referring to function_call(...args); or function call_me(...args) {}?

Gokul Kathirvel • Apr 6 '18

function_call(...args)

Meghan (she/her) • Apr 6 '18

That is a type of array destructuring and can be used to pass the elements of an array to a function.

const array = [ 4, 2 ];
const sixteen = Math.pow(...array);

is equivalent to

const sixteen = Math.pow(4, 2);
// or
const sixteen = Math.pow(array[0], array[1], /* ... */);

Gokul Kathirvel • Apr 6 '18

yeah, but in a component model, when handling functions, it becomes black box

passToAnotherFunc() {
  handleItSomewhere(...arguments);
}

now, I completely unaware of the argument list!

Meghan (she/her) • Apr 7 '18

the value of arguments here is the value of the arguments passed to passToAnotherFunc. See the deprecated arguments object

Antonin J. (they/them) • Apr 9 '18

Wait, the arguments isn't deprecated, it's only arguments.caller property that's non-standard and deprecated.

Shalvah • Aug 24 '18 • Edited

Combining Meghan's two earlier responses, a better way would be:

passToAnotherFunc(...args) {
  handleItSomewhere(...args);
}

But I feel it's unlikely you'd need to write this kind of code. Could you give a real-world example?

Meghan (she/her) • Aug 25 '18

@antjanus it's not deprecated per-se but it is disabled in strict and module mode.

@shalvah +1 because instead of calling passToAnotherFunc to call handleItSomewhere, why not just call handleItSomewhere?

Antonin J. (they/them) • Sep 5 '18

I had no idea it was disabled in strict/module mode!

Aral Roca • Apr 8 '18

Is useful, for example, if doesn't matter how many parameters receive the function:

const sum = (...numbers) => numbers.reduce((a, b) => a + b, 0);

sum(1, 4); // 5
sum(2, 3, 4); // 9

Nate • Sep 7 '18

Generally speaking you should only use it if you were writing some library i guess. Most of the time i just use it for debugging. But you're right that it would probably be buggy in most cases.