How to check for an undefined or null variable in JavaScript?

Question

We are frequently using the following code pattern in our JavaScript code

if (typeof(some_variable) != \'undefined\' && some_variable != null)
{
             


        

Answer 1

this is the only case in which == and != should be used:

if (val == null) console.log('val is null or undefined')

if (val != null) console.log('val is neither null nor undefined')