Question

I’ve always handled optional parameters in JavaScript like this:

function myFunc(requiredArg, optionalArg){   optionalArg = optionalArg || 'defaultValue';    // Do stuff } 

Is there a better way to do it?

Are there any cases where using || like that is going to fail?

Answer 1

Your logic fails if optionalArg is passed, but evaluates as false – try this as an alternative

if (typeof optionalArg === 'undefined') { optionalArg = 'default'; } 

Or an alternative idiom:

optionalArg = (typeof optionalArg === 'undefined') ? 'default' : optionalArg; 

Use whichever idiom communicates the intent best to you!