Angular.noop 是做什么用的？

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

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);

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);
}

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

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);
}

*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

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()"`}