What is the use of ? and :

Question

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JS How to use the ?: (ternary) operator

I download one plugin for wordpress in that plugin there is one javascript. Into that js code I don't understand how it works.

function ddet_javascript() {

echo '
<script language="JavaScript" type="text/javascript"><!-- 
function expand(param) { 
param.style.display=(param.style.display=="none") ? "" : "none"; 
 } 
  //--></script>';
}

In this code I don't understand the line given below.

param.style.display=(param.style.display=="none") ? "" : "none";

what is the use of ? and : in this line. please let me know if anyone know about it.

jQuery != JavaScript. There is no jQuery in this post. At all. — Ben Rowe, Aug 30 '12 at 05:32

score 3 · Accepted Answer · answered Aug 30 '12 at 05:32

3

It is an operator:

(condition) ? true : false

It is like:

if(param.style.display=="none")
       param.style.display="";
else
       param.style.display="none;

answered Aug 30 '12 at 05:32

ragklaat

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score 2 · Answer 2 · answered Aug 30 '12 at 05:30

2

This is ternary operator. it's works like if else statement.

view this link:

http://davidwalsh.name/learning-ternary-operators-tips-tricks

http://jqfundamentals.com/#example-2.16

answered Aug 30 '12 at 05:30

Hkachhia

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This link is really helpful for me to understand the ternary operator. – wasim kazi Aug 30 '12 at 05:43

score 2 · Answer 3 · answered Aug 30 '12 at 05:32

2

It's the ternary conditional operator: The expression

Cond ? a : b

evaluates Cond and lazily returns a if it was true, and otherwise returns b.

The entire result of the expression in your case is assigned to param.style.display. In other words, if display is already set to "none", it will be set to "", and otherwise it will be set to "none".

This operator is common in many languages, since it provides you with a single expression whose value is conditional on something.

answered Aug 30 '12 at 05:32

Kerrek SB

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I really want JavaScript to include a second ternary operator so everyone gets confused. (Just kidding, I only sort of want it) – ChaosPandion Aug 30 '12 at 05:33

score 2 · Answer 4 · answered Aug 30 '12 at 05:33

2

In your code it works like this:

if(param.style.display=="none"){
   param.style.display = "";  
} else{
    param.style.display = "none";  
}

answered Aug 30 '12 at 05:33

Codegiant

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is that clear to you @Wasim Kazi – Codegiant Aug 30 '12 at 05:36
ya Sandinp Now I'm clear that how we can use ternary operator in Jquery. – wasim kazi Aug 30 '12 at 05:44

score 1 · Answer 5 · answered Aug 30 '12 at 05:34

1

It is called conditional (ternary) operator.

test ? expression1 : expression2

If test is true, it returns the expression 1 else returns expression 2.

And this is not specific to jquery but a javascript operator.

For more info, ternary operator javascript

answered Aug 30 '12 at 05:34

Senthil Kumar

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+1 for getting the name right (ecma-international.org/ecma-262/5.1/#sec-8.4). :-) – RobG Aug 30 '12 at 06:05

score 0 · Answer 6 · answered Aug 30 '12 at 05:31

0

x=a?b:c, ?: is a ternary operator (works on 3 operands). It means if a is true then x=b else x=c

answered Aug 30 '12 at 05:31

Prashant

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score 0 · Answer 7 · answered Aug 30 '12 at 05:32

0

if (param.style.display=="none")
  param.style.display = "";
else
  param.style.display = "none";

answered Aug 30 '12 at 05:32

Victor

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What is the use of ? and :

7 Answers7