javascript check null or empty string

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, Jun 19 '18 at 13:50

score 20 · Answer 1 · answered Jun 19 '18 at 13:49

20

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 '18 at 13:49

Ankit Agarwal

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7

And zero..... so may not be the best option based on the input – epascarello Jun 19 '18 at 13:51
1

`javascript check null or empty string` OP says string value @epascarello – Ankit Agarwal Jun 19 '18 at 13:53
So when you have `value = '0';` then `!value` is `false` – Ankit Agarwal Jun 19 '18 at 13:54

score 1 · Answer 2 · answered Jun 19 '18 at 13:52

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 == "".

javascript check null or empty string

2 Answers2