Quick Answer

Resolve undefined identifier issues.

Understanding the Issue

TypeScript raises this error when it cannot locate a variable, function, or type declaration in the current scope.

The Problem

This code demonstrates the issue:

Typescript Error 
console.log(undeclaredVar); // Error

The Solution

Here's the corrected code:

Typescript Fixed 
// Solution 1: Declare the variable
const declaredVar = "Hello";
console.log(declaredVar);

// Solution 2: Import from another module
import { SomeName } from "./module";

// Solution 3: Check for typos
const userName = "John";
console.log(userName); // Not userNamme

// Solution 4: Add type definitions
npm install @types/library-name

Key Takeaways

Ensure all identifiers are properly declared, imported, or typed.