I want to be able to tell if a function is noop. I was looking for a built in method such as angular.isNoop() but couldn't find anything. Is there anything that differentiates a noop?

I want to be able to tell if a function is noop. I was looking for a built in method such as angular.isNoop() but couldn't find anything. Is there anything that differentiates a noop?

• javascript
• angularjs

Share Improve this question Follow edited Oct 14, 2015 at 19:02 Estus Flask 224k7979 gold badges472472 silver badges611611 bronze badges asked Oct 14, 2015 at 18:25 ialexanderialexander 9101010 silver badges2828 bronze badges 1

• well, if you're getting the noop from a shared location, they'd all contain the same function, thus allowing you to do an exactly equals check. Otherwise all you can do is look at the .toString() of the function. – Kevin B Commented Oct 14, 2015 at 18:29

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A noop is simply a function that contains no operations. You can test for a specific noop function by using ===

For example;

console.log(x === angular.noop);

Will print true if x was assign the noop from Angular, but this will not work if x is using the noop from jQuery.

To check if a variable looks like a noop. You just need to see if the function string ends with {}. You can try something like this.

console.log(angular.isFunction(x) && /\{\}$/.test(x.toString()));

The above should work even in the code is minified.

A noop function has a name just like any other function. That name is noop. So you can check for it just by calling:

var theFunction = angular.noop;
theFunction.name === 'noop'

It is not a typical task, it is unlikely that the framework will have one.

function isNoop(fn) {
  var trimRegex = /^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g;

  try {
    return !fn.toString().match(/{([\s\S]*)}$/)[1].replace(trimRegex, '');
  } catch (e) { };
}

It does not check for noop statements within function, of course. The credits for trimRegex go to jQuery.