javascript check null or empty string [duplicate]

Question

Why is this not possible?

var value = null;

if(value == (null || ""))
{
   //do something
}

I would like to check a value if it is null or empty without using the variable over and over again.

This is the way the language works. First of all, that expression in parentheses will evaluate to "", so it will check for that. That's how it works, and that's that. — Javid Asgarov
– Javid Asgarov, Commented Jun 19, 2018 at 13:50

Ankit Agarwal · Accepted Answer · 2018-06-19 13:49:49Z

21

Use !value. It works for undefined, null and even '' value:

var value = null;

if(!value)
{
  console.log('null value');
}

value = undefined;

if(!value)
{
  console.log('undefined value');
}

value = '';

if(!value)
{
  console.log('blank value');
}

answered Jun 19, 2018 at 13:49

Ankit Agarwal

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3 Comments

epascarello Over a year ago

And zero..... so may not be the best option based on the input

Ankit Agarwal Over a year ago

javascript check null or empty string OP says string value @epascarello

Ankit Agarwal Over a year ago

So when you have value = '0'; then !value is false

Some programmer dude · Accepted Answer · 2018-06-19 13:52:19Z

1

If we split the condition into its two relevant parts, you first have null || "". The result of that will be equal to the empty string "".

Then you have value == ""., which will be false if value is null.

The correct way to write your condition is value == null || value == "".

answered Jun 19, 2018 at 13:52

Some programmer dude

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