TypeScript errors look long, but the message is usually in the last line.
Direct answer
Read the error from the bottom up. Most beginner errors are one of three: a type mismatch ("not assignable"), a value that may be undefined, or a parameter with no type. Fix by correcting the type, checking the value or adding an annotation.
Common messages
| Message | Fix |
|---|---|
| Type 'string' is not assignable to type 'number' | Use the right type or convert it |
| Object is possibly 'undefined' | Check with if or use ?. |
| Parameter 'x' implicitly has an 'any' type | Add a type to the parameter |
| Property 'foo' does not exist on type | Add it to the type or fix the name |
| Cannot find name 'x' | Import it or check the spelling |
Example
const user = users.find(u => u.id === 1);
console.log(user.name); // possibly undefined
console.log(user?.name); // fixed
Where Teyro fits
Teyro's TypeScript for Beginners course turns this into short lessons you can play in a few minutes a day. It has 20 lessons, and you can start free.
The bottom line
The compiler is pointing at real mistakes. Read, fix, repeat.
