How to check if argument is defined in function definition in JavaScript?

Question

For example if I have a function defined like this:

function set_name(name) {
    return name;
}

But I call it this way (for personal reasons this way):

set_name.apply(this, ['Duvdevan', 'Omerowitz']);

What would be the best practice to check and prevent set_name function's further execution if it had accepted more than 1 parameter / argument?

Also, I have to note that I'm trying to figure out a way to check this before I call .apply function:

function set_name(name) {
    // if(arguments.length > 1) console.log('This is not what I need though.');

    return name;
}

var args = ['Duvdevan', 'Omerowitz'];

// Now, at this point I'd like to check if the set_name function can accept two arguments.
// If not, I'd console.log or return new Error here.

set_name.apply(this, args);

Is this doable?

So if it has more than one argument, you want it to not run? Only way would be the if like you coded it... — epascarello
– epascarello, Commented Nov 10, 2016 at 21:57

TimoStaudinger · Accepted Answer · 2016-11-10 21:57:31Z

3

You can get the number of arguments expected by the function via Function.length:

function set_name(name) {
  return name;
}

var args = ['Duvdevan', 'Omerowitz'];

console.log(set_name.length);         // 1

if (args.length > set_name.length) {
  throw new Error('Too many values'); // throws
}

set_name.apply(this, args);           // not executed

answered Nov 10, 2016 at 21:57

TimoStaudinger

42.7k16 gold badges91 silver badges96 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Zlatan Omerovic Over a year ago

Pretty damn awesome! Actually, I was afraid that I'd have to do set_name.toString() and parse the actually function definition for defined arguments ... but this, you're a JavaScript Gandalf! Thanks!

Collectives™ on Stack Overflow

How to check if argument is defined in function definition in JavaScript?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related