The meaning of type in javascript

Type in Javascript means the data type of the variable. In Javascript, each variable has its own data type, which can be divided into two categories: basic types and reference types.

First of all, there are five basic types: number, string, boolean, null, and undefined.

1. number type

The Number type is used to represent numbers, including integers and floating point numbers. Its value range is plus or minus 2 raised to the 53rd power. It can be passed through isNaN () function determines whether a value is a numeric type.

2. string type

The String type is used to represent text strings and can contain any characters. The length of the string can be obtained through the length attribute.

3. boolean type

The Boolean type has only two values, true and false, used to represent true and false values.

4. null type

null represents an empty object, and the type of null is object.

5. undefined type

undefined represents an undefined value, usually used to indicate that a variable has not been assigned a value or a property does not exist.

Reference type

Reference type represents complex data through objects. It has the following types: Array, Object, Function, etc.

1. Array type

The Array type is a special object that can store an ordered collection. Array type elements can be any type of data, and the number of elements can be obtained through the Array.length property.

2. Object type

The Object type is a basic type in Javascript. It can represent anything, that is, its value can be any type of data. The Object type is an unordered collection, and the properties in the object can be of any value type.

3. Function type

The Function type is a special object that has the ability to execute code, accept parameters and return values. In Javascript, a function is a data type that can be assigned to a variable or passed as a parameter to other functions.

Summary

In Javascript, the type of variables is very important. Since Javascript is a dynamic weakly typed language, the variable type may change as the program runs, so we need to Consider and judge the type of variables. Reasonable use of variable types in programs can improve the performance and maintainability of the program and better implement business logic.

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