What kind of if statement is this?

Question

So I used an online JavaScript optimizer and it did something strange to my IF statements that is new to me.

{1===a?window.addEventListener("scroll",turnOff):0===a&&window.removeEventListener("scroll",turnoff)}

What in the world is this? Help me to understand the parts of it please.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator — jayelm, Sep 28 '14 at 23:55
It's a [conditional ('ternary') operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator). — David says reinstate Monica, Sep 28 '14 at 23:55

killQuotes · Accepted Answer · 2014-09-29T00:07:18.083

1

The three equal signs are a representation of strict comparison operators. Unlike the usual double equal signs, using === compares both the type and value of the expressions being compared. Both the type and value must be equal for the statement to evaluate to true.

The ? and : are shorthand versions of the if statement. When 1===a is true, the statement after the question mark is evaluated. Otherwise, the statement after the colon is evaluated. This shorthand version of the if statement is known as a Conditional (or Ternary) operator.

edited Sep 29 '14 at 00:07

answered Sep 29 '14 at 00:01

killQuotes

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Thank you, these are all great answers but yours was sorta dumb down for me XD So can you tell me the purpose of &&? why is it 0===a&& and not 0===a? ? – Sebastian Sep 29 '14 at 00:11
@Sebastian: Read a beginner's tutorial, and you'll learn all about the basic JavaScript operators. – Sep 29 '14 at 00:16
I did :3 I know its obviously and (and) operator but what is its purpose in this statement. Andddd as I was typing this I just got it.. lmao. But to be on the safe side, its also checks if 0===1 then && is saying also do this if its found true. Otherwise neither statement is used? – Sebastian Sep 29 '14 at 00:21
Here's how it evaluates...if "1===a" is false, "0===a" will evaluated and "window.removeEventListener("scroll",turnoff)" will be invoked, which has no return value, so whatever "0===a" returns will be what is returned from the expression. – killQuotes Sep 29 '14 at 00:53
thank you, and so I tried running simple code in a test, like b.innerHTML. where b was an id element. it works in the true statement but I could only get functions to work in the second statment. why wouldnt b.innerHTML work in false but it does in true? – Sebastian Sep 30 '14 at 09:16

score 0 · Answer 2 · answered Sep 28 '14 at 23:58

0

The ? Operator is used just as an if.

if(a){
   b;
} else {
   c;
}

is equal to

a ? b : c;

answered Sep 28 '14 at 23:58

Grochni

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symlink · Answer 3 · 2014-09-29T00:44:53.143

0

It's called a ternary operator. It compares the condition

if a === 1

and returns the first result if the condition is true:

window.addEventListener("scroll",turnOff)

and the second if false:

0===a&&window.removeEventListener("scroll",turnoff)

This line of code does two things, sets a equal to 0 and removes an event listener.

See this tutorial

edited Sep 29 '14 at 00:44

answered Sep 29 '14 at 00:03

symlink

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score -1 · Answer 4 · edited May 23 '18 at 14:42

-1

It is a Conditional (Ternary) operator.

You can read more about ternary operators at the developer Mozilla docs:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator

It is structured like this:

condition ? code if true : code if false

edited May 23 '18 at 14:42

Mathias Rechtzigel

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answered Sep 29 '14 at 00:00

kjr1995

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What kind of if statement is this?

4 Answers4