Is there a "null coalescing" operator in JavaScript?

Question

Is there a null coalescing operator in Javascript?

For example, in C#, I can do this:

String someString = null; var whatIWant = someString ?? "Cookies!"; 

The best approximation I can figure out for Javascript is using the conditional operator:

var someString = null; var whatIWant = someString ? someString : 'Cookies!'; 

Which is sorta icky IMHO. Can I do better?

Answer 1

Update

JavaScript now supports the nullish coalescing operator (??). It returns its right-hand-side operand when its left-hand-side operand is null or undefined, and otherwise returns its left-hand-side operand.

Old Answer

Please check compatibility before using it.

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The JavaScript equivalent of the C# null coalescing operator (??) is using a logical OR (||):

var whatIWant = someString || "Cookies!"; 

There are cases (clarified below) that the behaviour won't match that of C#, but this is the general, terse way of assigning default/alternative values in JavaScript.

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Clarification

Regardless of the type of the first operand, if casting it to a Boolean results in false, the assignment will use the second operand. Beware of all the cases below:

alert(Boolean(null)); // false alert(Boolean(undefined)); // false alert(Boolean(0)); // false alert(Boolean("")); // false alert(Boolean("false")); // true -- gotcha! :) 

This means:

var whatIWant = null || new ShinyObject(); // is a new shiny object var whatIWant = undefined || "well defined"; // is "well defined" var whatIWant = 0 || 42; // is 42 var whatIWant = "" || "a million bucks"; // is "a million bucks" var whatIWant = "false" || "no way"; // is "false"