Javascript Ternary operator with empty else

Question

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

why are you using a ternary operator if there is no other branch of logic? — Jon Wells
– Jon Wells, Commented Aug 12, 2015 at 9:07
The ternary operator is called ternary because it requires three operands to operate. What I think would be a more appropriate solution is to use JavaScript short-circuits. Please take a look at my humble posting about JavaScript short-circuits @ js-guru.blogspot.com/2015/08/javascript-short-circuiting.html — Allan Chua
– Allan Chua, Commented Aug 12, 2015 at 9:09
no need of using ternary operator if you dont have else. ternary is short hand method for if-else. — Sindhoo Oad
– Sindhoo Oad, Commented Aug 12, 2015 at 9:10
Dont you think you are making things Wayyy complicated than you need to ? — Pratik Joshi
– Pratik Joshi, Commented Aug 12, 2015 at 9:10
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 — Probosckie
– Probosckie, Commented Aug 12, 2015 at 9:16

Nina Scholz · Accepted Answer · 2015-08-12 09:18:50Z

11

Answer to your real question in the comments:

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

answered Aug 12, 2015 at 9:18

Nina Scholz

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Comments

Pratik Joshi · Accepted Answer · 2015-08-12 09:15:43Z

8

Do this :

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

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

edited Aug 12, 2015 at 9:15

Pratik Joshi

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answered Aug 12, 2015 at 9:07

potatopeelings

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1 Comment

Probosckie Over a year ago

I am actually trying to do something else. The above example was just a base case. I want to parse an array (variable name - all2) and push an element of all2 into another array only if it is non-null

user3165588 · Accepted Answer · 2015-08-12 09:17:14Z

5

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);

answered Aug 12, 2015 at 9:17

user3165588

Comments

MoLow · Accepted Answer · 2015-08-12 09:14:13Z

4

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)

edited Aug 12, 2015 at 9:14

answered Aug 12, 2015 at 9:11

MoLow

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1 Comment

Nina Scholz Over a year ago

the parentheses of the comparison are not necessary

4b0 · Accepted Answer · 2020-04-08 10:19:05Z

3

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.

edited Apr 8, 2020 at 10:19

4b0

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answered Apr 8, 2020 at 10:05

James M

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Comments

Milos Sretin · Accepted Answer · 2015-08-12 09:12:37Z

2

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);

answered Aug 12, 2015 at 9:12

Milos Sretin

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Comments

venkat7668 · Accepted Answer · 2015-08-12 09:13:07Z

2

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");

answered Aug 12, 2015 at 9:13

venkat7668

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