TS2454 — Variable Used Before Assignment

O que causa este erro

TypeScript detected that a variable might not have been assigned a value before it is read. This happens when a variable is declared without an initializer and only assigned in some code paths.

Como corrigir

Initialize the variable when you declare it. Ensure all code paths assign a value before the variable is used. Use the definite assignment assertion (!) if you know the value will be assigned before use.

let x: string;
console.log(x);