How can I set a javascript variable to "" if it is undefined?

Question

I have the following:

var viewID = $(link).data('dialog-id')

This works when there is a dialog-id value. But when there is no value then viewID gets the value of "undefined".

Is there a way that I can make the value of viewID be equal to an empty string if dialog-id is not available or be equal to dialog-id if it is available?

Paolo Bergantino · Accepted Answer · 2012-02-15 15:30:35Z

6

You can do:

var viewID = $(link).data('dialog-id') || '';

Which works thanks to the way Javascript handles short-circuit evaluation.

answered Feb 15, 2012 at 15:30

Paolo Bergantino

490k83 gold badges523 silver badges437 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Colin Brock · Accepted Answer · 2012-02-15 15:32:12Z

3

var viewID = $(link).data('dialog-id') == undefined ? "" : $(link).data('dialog-id');

edited Feb 15, 2012 at 15:32

Colin Brock

21.6k9 gold badges51 silver badges62 bronze badges

answered Feb 15, 2012 at 15:29

Hungry Beast

3,7449 gold badges54 silver badges76 bronze badges

Comments

Feysal · Accepted Answer · 2012-02-15 15:31:12Z

0

Alternately:

var viewID = $(link).data('dialog-id')
if (viewID == null) {
    viewID = '';
}

This also works, since undefined and null are considered equal.

answered Feb 15, 2012 at 15:31

Feysal

6234 silver badges7 bronze badges

Comments

JaredPar · Accepted Answer · 2012-02-15 15:32:58Z

0

The easiest way is to use the || operator

var viewID = $(link).data('dialog-id') || '';

The '||' operator takes a value on the left and right. If the value on the left is truthy then it will be returned else the right value will be. The value undefined is falsy hence if it's returned from the data('dialog-id') call then it will pick '' instead

answered Feb 15, 2012 at 15:32

JaredPar

759k152 gold badges1.3k silver badges1.5k bronze badges

Collectives™ on Stack Overflow

How can I set a javascript variable to "" if it is undefined?

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related