TypeScript Type Not Assignable Error

Hover over the error in your IDE to see the exact type mismatch. The error message shows both the expected type and the type you're providing.

// Error: Type "string" is not assignable to type "number"
const age: number = "25" // ❌
const age: number = 25    // ✅

Use type guards to narrow types before using them.

function process(value: string | number) {
  // ❌ Error: toUpperCase() not on number
  // return value.toUpperCase()
  
  // ✅ Type guard
  if (typeof value === "string") return value.toUpperCase()
  return value.toFixed(2)
}

Ensure objects include all required properties from the type or interface.

interface User {
  id: number
  name: string
  email: string
}

// ❌ Missing email property
const user: User = { id: 1, name: "John" }

// ✅ All required properties
const user: User = { id: 1, name: "John", email: "john@example.com" }