Variables and Type Annotations
Explore how TypeScript enhances JavaScript by allowing you to add type annotations to variables. Learn to prevent common bugs by specifying data types explicitly, improving code reliability and clarity. This lesson helps you understand type inference, type annotation syntax, and practical examples of type enforcement.
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That last section was a little on the abstract side, let’s talk more concretely.
TypeScript allows you but does not require you, to annotate your JavaScript code with information about the types of various pieces of data in the code.
TypeScript uses this information as a constraint on the values that those pieces of data can contain. If you declare a variable to be a number, and then assign it the value "3", the TypeScript compiler will complain and will not allow the code to be compiled.
If you don’t add any explicit type information, however, you don’t get the full benefit of using TypeScript. It will still catch some errors, such as assigning two different types of values to the same variable or if you try to send a function the wrong number of arguments. By adding as much type ...