JavaScript null check

Question

I\'ve come across the following code:

function test(data) {
    if (data != null && data !== undefined) {
        // some code here
    }
}
         


        

Answer 1

In your case use data==null (which is true ONLY for null and undefined - on second picture focus on rows/columns null-undefined)

function test(data) {
    if (data != null) {
        console.log('Data: ', data);
    }
}

test();          // the data=undefined
test(null);      // the data=null
test(undefined); // the data=undefined

test(0); 
test(false); 
test('something');

Here you have all (src):

if

== (its negation !=)

=== (its negation !==)