What is "?:" notation in JavaScript?

I found this snippet of code in my travels in researching JSON:

var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray; 

I'm seeing more and more of the ? and : notation. I don't even know what it is called to look it up! Can anyone point me to a good resource for this? (btw, I know what != means).

4 Answers

It's called a Conditional (ternary) Operator. It's essentially a condensed if-else.

So this:

var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray; 

...is the same as this:

var array; if (typeof objArray != 'object') { array = JSON.parse(objArray); } else { array = objArray; } 

It's the ternary conditional operator -- basically,

if (condition) { a = 4; } else { a = 5; } 

becomes

a = condition ? 4 : 5; 

That’s called the conditional operator:

condition ? expr1 : expr2 

If condition is true, the operator returns the value of expr1; otherwise, it returns the value of expr2.

Just read it like this:

result = (condition) ? (true value) : (false value); 

place what ever you like in the 3 operators.

As many has compared it to an IF.. THEN structure, so it is.