Undefined is a special value not a string!

Recently I came across this statement

 if (val != 'undefined' && val != null && val != 'null') {
//some statements
}

undefined and null are simple types and not literal strings!

alert(null === ‘null’); will return false so will alert(undefined === ‘undefined’);

So the statement should be:

 if (val !== undefined && val !== null) {
//some statements
}
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