Angularjs brackets syntax

Question

I was reading https://docs.angularjs.org/api/ng/function/angular.noop which has this example:

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

I can't work out what this line is doing:

  (callback || angular.noop)(result);

It looks like callback and angular.noop are functions that can return true or false, but what is the value used for, and what does (result) do next to it?

charlietfl · Accepted Answer · 2020-10-14 01:33:44Z

1

The left side determines which function reference to use and the right side invokes that function passing in result as parameter

In more verbose form it is the same as doing:

if (callback) {
  callback(result)
} else {
  angular.noop(result)
}

answered Oct 14, 2020 at 1:33

charlietfl

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3 Comments

David Klempfner Over a year ago

So it calls callback, which returns true or false, and then if it's true, it once again calls callback passing in result as the argument?

charlietfl Over a year ago

More like using the outer function with or without passing in a callback. foo() vs foo(function(result){ /* do something*/})

David Klempfner Over a year ago

I understand now. The callback in the if statement is not being called (because it doesn't have () after it), it's just being tested for null/undefined. If it's not null/undefined then it will be called with result as the argument.

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