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

In ES5 or ES6 if you need check it several times you cand do:

const excluded = [null, undefined, ''];

if (!exluded.includes(varToCheck) {
  // it will bee not null, not undefined and not void string
}