The compiler will then check the types (where possible) during compilation and report type errors. The type is written after a colon following the variable name, like this: You can add type declarations to variables, function parameters and function return types.

This strong typing and object orientation makes TypeScript easier to debug and maintain, and those were two of the weakest points of standard JavaScript. For instance, when a TypeScript variable is declared as a number, you cannot assign a text value to it. The strong typing also means that the language can (and is) precompiled and that variables cannot be assigned values that are out of their declared range. This means that TypeScript code tends to be easier to use for large projects and that code tends to be easier to understand and maintain. TypeScript makes JavaScript more like a strongly-typed, object-oriented language akin to C# and Java. TypeScript adds a lot of new features on top of that.

TypeScript is a typed superset of JavaScript, which means that all JavaScript code is valid TypeScript code.

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