If it is undefined, it will not be equal to a string that contains the characters "undefined", as the string is not undefined. You can check the type of the variable:

Feb 22, 2011 · NaN. See for yourself. console.log (null-undefined). The difference between null and undefined is NaN. (Note that this is an attempt at humour, before you flame me for …

I can't find any difference between typeof somevar == 'undefined' and typeof somevar === 'undefined', because typeof always returns string. For null it will return 'object'. Or could be that …

While literally using the keyword undefined, Boolean(undefined) works, trying that with an undefined variable doesn't work, and that is the whole point of doing the check for null or …

typeof MyVariable == 'undefined' doesn't discern between an initialized variable with an undefined value and an undeclared variable unless the variable was initially declared and initialized to …

I'm using some destructuring like this: const { item } = content console.log(item) But how should I handle content === undefined - which will throw an error? The 'old' way would look like this: ...

If you want to find the difference between an undefined property p of an object o, and a property p that has defined and set to undefined, you have to use the 'p' in o operator.

Limitations and warnings Depending on how Javascript is implemented. It is possible that undefined will be converted to null instead of just being removed. Nested Object, Array will be …

0 undefined and false are distinct values. false is a defined Boolean value, while undefined signifies the absence of a value.

48 SIMPLE ANSWER Although Typescript is a strongly typed language, it has the same problems with pointers and variables initialization inherited from Javascript. Javascript doesn't check …