The value to check
true if the value is null or undefined
isNullOrUndefined(null); // true
isNullOrUndefined(undefined); // true
isNullOrUndefined("undefined"); // true
let value = null;
isNullOrUndefined(value); // true
let value = undefined;
isNullOrUndefined(value); // true
isNullOrUndefined(""); // false
isNullOrUndefined(0); // false
isNullOrUndefined(new Date()); // false
isNullOrUndefined(true); // false
isNullOrUndefined(false); // false
Checks if the provided value is null, undefined or contains the string value of "undefined".