JavaScript style for optional callbacks

javascript coding-style callback
henry.oswald picture henry.oswald · Jul 22, 2011 · Viewed 56.1k times · Source

I have some functions which occasionally (not always) will receive a callback and run it. Is checking if the callback is defined/function a good style or is there a better way?

Example:

function save (callback){
   .....do stuff......
   if(typeof callback !== 'undefined'){
     callback();
   };
};

Answer

Raynos picture Raynos · Jul 22, 2011

I personally prefer

typeof callback === 'function' && callback();

The typeof command is dodgy however and should only be used for "undefined" and "function"

The problems with the typeof !== undefined is that the user might pass in a value that is defined and not a function

Related questions

What are the benefits to using anonymous functions instead of named functions for callbacks and parameters in JavaScript event code?

I'm new-ish to JavaScript. I understand many of the concepts of the language, I've been reading up on the prototype inheritance model, and I'm whetting my whistle with more and more interactive front-end stuff. It's an interesting language, but I'm …

Read More
typeof !== "undefined" vs. != null

I often see JavaScript code which checks for undefined parameters etc. this way: if (typeof input !== "undefined") { // do stuff } This seems kind of wasteful, since it involves both a type lookup and a string comparison, not to mention its verbosity. …

Read More
What's the best way to convert a number to a string in JavaScript?

What's the "best" way to convert a number to a string (in terms of speed advantage, clarity advantage, memory advantage, etc) ? Some examples: String(n) n.toString() ""+n n+""

Read More