The never type is a subtype of, and assignable to, every type however, no type is a subtype of, or assignable to, never (except never itself). JavaScript Data types are used to identify the type of data that is stored inside a variable during the script execution. Variables also acquire the type never when narrowed by any type guards that can never be true. Numeric type Unlike strong types of languages such as C, Java, JavaScripts numerical types not only include all plastic variables, but also all floating point variables. The never type represents the type of values that never occur.įor instance, never is the return type for a function expression or an arrow function expression that always throws an exception or one that never returns. JavaScript basic data types have the following five (1) Value type (2) Boolean type (3) String type (4) Undefined Type (5) NULL type 1. Union types are an advanced topic that we’ll cover in a later chapter.Īs a note: we encourage the use of strictNullChecks when possible, but for the purposes of this handbook, we will assume it is turned off. Object, Array, and Function (which are all types of objects) are composite data types. String, Number, and Boolean are primitive data types. In cases where you want to pass in either a string or null or undefined, you can use the union type string | null | undefined. There are six basic data types in JavaScript which can be divided into three main categories: primitive (or primary), composite (or reference), and special data types. ![]() The syntax for a basic if statement is as follows. 1. However, when using the strictNullChecks flag, null and undefined are only assignable to unknown, any and their respective types (the one exception being that undefined is also assignable to void). means that a JavaScript variable can hold a value of any data type. In this article, we will understand what they are. That means you can assign null and undefined to something like number. JavaScript also has various data types which are arrays, functions, strings, numbers, booleans and others. ![]() ![]() 100 Boolean, represents boolean value either false or true Undefined, represents. By default null and undefined are subtypes of all other types. JavaScript primitive data types Number, represents numeric values e.g.
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