Why passing extra arguments to a function works in JavaScript?

Question

Let's say I've defined a function :

function myAwesomeFunction(x){
    console.log(x);
}

now, what I expect is, if I'll call it like this: myAwesomeFunction(1) or myAwesomeFunction('lol') or myAwesomeFunction('whatever'), it'll work and it does.

but how does it work, even when I pass extra arguments to the function and simply ignores all arguments except the first one :

myAwesomeFunction('why so', 'serious?')

we don't even have any optional arguments in the above function?(i.e, like (x, y=''))

function myAwesomeFunction(x){
    console.log(x);
}

myAwesomeFunction(1);
myAwesomeFunction('lol');
myAwesomeFunction('whatever');
myAwesomeFunction('why so', 'serious?')
myAwesomeFunction('why', 'so', 'serious?')

Because that's how the language has been designed. That's like asking why a variables is declared by writing `var x;` and not `variable x;`. — Ingo Bürk, Nov 02 '17 at 20:17
Read this answer by @Prinzhorn https://stackoverflow.com/questions/12694031/what-happens-if-i-call-a-js-method-with-more-parameters-than-it-is-defined-to-ac — Sanchit Patiyal, Nov 02 '17 at 20:27
was looking for an answer like [this](https://stackoverflow.com/a/12694124/6518605) not [this](https://stackoverflow.com/questions/47083910/why-passing-extra-arguments-to-a-function-works-in-javascript/47084109#comment81117067_47083910) @IngoBürk — Ashish Ranjan, Nov 02 '17 at 20:35

score 6 · Answer 1 · answered Nov 02 '17 at 20:22

You can call a Javascript function with any number of parameters, regardless of the function's definition.

Any named parameters that weren't passed will be undefined.

Javascript treats your parameters as an array. More specifically it's the arguments array, Named parameters in function declarations are just pointers to members of arguments. More info here

score 0 · Answer 2 · answered Nov 02 '17 at 20:28

When you defined the function, you gave it one parameter x

The language is designed to look for a single argument for each parameter, and ignore the others.

However, you are able to access the other arguments via the special arguments object.

Try typing console.log(arguments) within your function body and seeing what happens...

Why passing extra arguments to a function works in JavaScript?

2 Answers2