JavaScript, by nature, is described as a dynamically typed language. This means that any particular variable can hold a number of data types, including numbers, strings, arrays, objects, and functions. The type of a variable in JavaScript is determined by assignment. This means that when we assign a value to a variable, the JavaScript runtime interpreter determines the type of that variable.
However, the JavaScript runtime can also reassign the type of a variable depending on how it is being used, or on how it is interacting with other variables. It may assign a number to a string, for example, in certain cases.
Let's take a look at an example of this dynamic typing in JavaScript and what errors it can introduce. Then, we will explore the strong typing that TypeScript uses and its basic type system.