CODEWITHSUNDEEP
javascriptif-statementternary
Probosckie
Probosckie

Reputation: 1812

Javascript Ternary operator with empty else

I'm trying to convert the following if-else to it's ternary operator representation in javascript as follows

var x = 2;
if (x === 2) {alert("2");}
else
         { //do nothing}

But when I do this:

(t==2)?(alert("1")):();

Chrome throws a SyntaxError.

My question is - How to have a ternary operator in javascript with an empty "else" branch - i.e the part that comes after ":". Also, is this allowed- using a ternary operator in javascript to execute statements - NOT do assignment.

Also: the above code was just a base case. I'm actually trying to get all the DOM elements of the page as an array (called all2) and then add only those elements to another array (called only) only if they have non-null class names. Here is my code: 

all2.forEach(function(e){ e.getAttribute("class") ? (only.push(e.getAttribute("class"))) : (); });

If I leave the third operand blank, it throws a syntax error. Passing a null works

Upvotes: 10

Views: 31841

Answers (7)

James M
James M

Reputation: 31

I don't like it's either. So you're on the right track looking for alternatives.

In this case, I would write:

t===2 && alert("2")

Your idea is valid too, for instance you can do this:

t===2 ? alert("2") : null

But it's four extra chars.

Upvotes: 3

Nina Scholz
Nina Scholz

Reputation: 386766

Answer to your real question in the comments:

all2.forEach(function (e) {
    e.getAttribute("class") && only.push(e.getAttribute("class"));
});

Upvotes: 11

user3165588
user3165588

Reputation:

You putted a lot of useless parentheses, and the best NULL value in js is undefined.

document.getElementById('btn-ok').onclick = function(){
  var val = document.getElementById('txt-val').value;
  
  val == 2 ? alert(val) : undefined;
}
<input id="txt-val" type="number" />
<button type="button" id="btn-ok">Ok</button>

using a single line if statement is better though

if(value === 2) alert(value);

Upvotes: 5

potatopeelings
potatopeelings

Reputation: 41075

Do this :

(t==2)?(alert("1")):null;

You could replace null by any expression that has no side effect. () is not a valid expression.

Upvotes: 7

MoLow
MoLow

Reputation: 3084

you have a few options to do this nicely in one line:

option1 - noop function

set a global noop function:

function noop(){}
(t==2)?(alert("1")):(noop());

option2 - && operator

when you use && operater, operands are evaluted only if previos ones where true, so you could miply write:

(t==2) && alert("1");

or, for exapmle if you have an arry you want to push to, you could test it is not null before:

arr && arr.push(obj)

Upvotes: 4

venkat7668
venkat7668

Reputation: 2777

NO, you can't have empty else, better don't use the ternary operator, it requires a third argument. Go with simple if condition.

if(t==2) alert("2");

Upvotes: 2

Milos Sretin
Milos Sretin

Reputation: 1748

In that case you don't need to use Ternary operator. Ternary operator requires a third argument.

condition ? expr1 : expr2

Lokki at Conditional (ternary) Operator

You can use the if statement

if ( t == 2 ) alert(1);

Upvotes: 2

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