TypeScript in Depth · Type Basics · Lesson 1 of 16
Adding Types to Variables
Concept
Adding Types to Variables
TypeScript lets you annotate variables with a type. The compiler then catches mismatched values before you run the code.
By the end of this lesson
- Explain the core idea behind Adding Types to Variables.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Adding Types to Variables. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Declare a boolean variable with an explicit type and assign it a value.
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