How to check undefined in Typescript

Question

I am using this code to check undefined variable but it\'s not working.

Answer 1

From Typescript 3.7 on, you can also use nullish coalescing:

let x = foo ?? bar();

Which is the equivalent for checking for null or undefined:

let x = (foo !== null && foo !== undefined) ?
    foo :
    bar();

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#nullish-coalescing

While not exactly the same, you could write your code as:

var uemail = localStorage.getItem("useremail") ?? alert('Undefined');