How do you check if a variable is undefined in TypeScript? I am looking for ways to resolve typescript check if undefined

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1

How do you check if a variable is undefined in TypeScript? I am looking for ways to resolve typescript check if undefined.

2

Hello Isha tantia,

Using typeof Operator: The typeof operator is a safe way to check if a variable is undefined because it avoids reference errors if the variable has not been declared.

let variable: any;
if (typeof variable === 'undefined') {
    console.log('Variable is undefined');
}
3

Hey Isha,

Direct Comparison: You can directly compare the variable to undefined. This method works if the variable has been declared but may be undefined.

let variable: number | undefined;
if (variable === undefined) {
    console.log('Variable is undefined');
}
4

Hello Isha,

Using Optional Chaining: If you want to check for undefined in a nested property or function result, you can use optional chaining combined with a check for undefined.

interface User {
    name?: string;
}
const user: User = {};
if (user.name === undefined) {
    console.log('User name is undefined');
}

This is particularly useful when dealing with objects where properties might be undefined.