What is Angular.noop used for?

Question

I have tried searching it everywhere even on Angular.org documentation but couldn't find any detailed explanation with implementation. It would be hugely helpful if any could explain it.

Knee

it's just an empty function that does nothing – Phosphatize

That much I got already. But why do we use it like this? "success = success || angular.noop;" – Knee

looks like @lechariotdor has got the better answer...you might move your acceptance so visitors to this page are more quickly directed to the best answer – Snap

Answer 1

angular.noop is an empty function that can be used as a placeholder when you need to pass some function as a param.

function foo (callback) {
    // Do a lot of complex things

    callback();
}

// Those two have the same effect, but the later is more elegant
foo(function() {});
foo(angular.noop);

Peccant

What's the benefit of calling noop rather than just leaving the function blank? Aesthetics, performance or something else? – Negus

@Negus It is more aesthetically pleasing and a good practice to use angular.noop as you always reuse the same empty function (instead of declaring a new anonymous function everytime). Performance-wise it makes no difference as the code for angular.noop is just an empty function named noop. – Peccant

Using angular.noop creates a strong coupling with angular object. I do prefer using inline anonymous function when is necessary. – Babb

Great thanks :) Can you explain what is $timeout(angular.noop)? – Banket

Answer 2

I find it extremely helpful when writing a function that expects a callback.

Example:

function myFunction(id, value, callback) {

    // some logic
    return callback(someData);
}

The function above will return an error, when it gets called without specifying the third argument. myFunction(1, 'a');

Example (using angular.noop):

function myFunction(id, value, callback) {

    var cb = callback || angular.noop; // if no `callback` provided, don't break :)
    // some logic
    return cb(someData);
}

Telephotography

Or you have a one-liner for that : typeof callback === 'function' && callback();. Way more classy ^^. Not using angular.noop though. – Prior

Answer 3

It is a function that performs no operations. This is useful in situation like this:

function foo(y) {
   var x= fn();
   (y|| angular.noop)(x);
 }

It is useful when writing code in the functional style

Woden

Ok. Got it thanks. But just a little query that why can't we simply do "(y)(x)" instead of "(y|| angular.noop)(x);"? What is the reason behind this? – Knee

@AngularHarsh:- You may write that. May be this example will help:- //do nothing on the success callback, hence replacing the success callbck function with angular.noop() $scope.contacts= Contacts.query( angular.noop,function(response) { Window.myresp = response; $scope.displayError(response); console.log("bad boy, listContacts failed"); }); – Woden

I think I got it now. So what we are doing here is displayError is triggered on failure but nothing happens on success(as suggested). – Knee

Answer 4

*this answer assumes that u are not a beginner in angular

Angular.noop is an empty function that can be used as placeholder in some cases

for example:

Imagine you are using q.all which do multiple calls to the api and return one promise. If some of these calls fail but u still need to handle the ones that didnt fail, use angular noop as a callback to the api calls when u catch the calls. If u dont use angular noop, q.all will reject everthing if one call fails.

Q.all( somecall.catch(angular.noop), anothercall).then( resolve result[0] and result[1])

If a call fails, Angular will ignore that and perform another call (but u will still will undefined for the first resolved result)

I Hope that I helped

Puppy

I downvoted because your answer is so grammatically and formally wrong I couldn't actually get any reliable information from it. – Orelle

Answer 5

var result = (callback || angular.noop)(params)

Its a shortest way to do

var result = typeof callback === 'function' && callback(params);

Taking into account that callback var will be a function

Mantilla

this is elegant – Scutum

Answer 6

If you want official documentation here is the link. It is pretty simple. I have also pasted the current documentation from link.

---

A function that performs no operations. This function can be useful when writing code in the functional style.

function foo(callback) {
  var result = calculateResult();
  (callback || angular.noop)(result);
}

---

Robbins

Answer 7

Trick: You can also use it to add a ternary to an ng-click attribute:

ng-click="(variable) ? doSomething() : angular.noop()"

_{Until I found out you could use ng-click="variable && doSomething()"`}

Improvisator

ng-click="(variable) ? doSomething() : true" would also work – Activist

ng-click="(variable) ? doSomething() : '' " would also work – Puppy