ts check if undefined or null. A method returns undefined if a value was not returned. Therefore, it returns false on numbers that are NaN, Infinity or -Infinity.
TypeScript is basically telling us that the emp.salary property might have a value of undefined, .
Undefined. The . Description. xyz === void 0. typeof xyz === 'undefined'. Use 2 for binary, 8 for octal, 10 for decimal & 16 for HexaDecimal number. null is a variable that is defined but is missing a value.
Number.isNaN returns whether the given value equals NaN. undefined is a variable that refers to something that doesn't exist, and the variable isn't defined to be anything. Double NOT operator.
If both operands are objects, return true only if they refer to the same object. The data type takes two forms: Just A Maybe that contains a value.