Building a type-safe dictionary in TypeScript

What is a type-safe dictionary?

In a programming language, a dictionary is a typical data structure that stores data in key-value pairs. JavaScript dictionary creation strategies offer a way to create a dictionary structure that accepts dynamic data types.

For example, a simple dictionary you’ve created in JavaScript may accept even objects as values even though you might use it for storing numbers. Using TypeScript type-checking features, you can turn these dynamic JavaScript dictionaries into type-safe dictionaries that accept only a pre-defined key-value type declaration, i.e., string for keys, and number for values.

A type-safe dictionary triggers compile-time and linter errors if a developer tries to store data types that are not defined in accepted dictionary key-value types.

As mentioned earlier, JavaScript has several ways to create dictionaries. Let’s learn them first before making them type-safe with TypeScript.