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This article introduces the relevant knowledge of "what are the data types of JavaScript". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

Data types refer to the types of values that can be stored and manipulated in a program. each programming language has its own supported data types, and different data types are used to store different data, such as text, values, images, and so on.

JavaScript is a dynamically typed language. When defining variables, you do not need to specify the type of variables in advance. The types of variables are dynamically determined by the JavaScript engine while the program is running. In addition, you can use the same variable to store different types of data, such as:

Var a; / at this time an is Undefineda = "http://c.biancheng.net/"; / / at this time an is String type a = 123; / at this time an is Number type

Data types in JavaScript can be divided into two types:

Basic data types (value types): string (String), number (Number), Boolean (Boolean), empty (Null), undefined (Undefined), Symbol

Reference data types: object (Object), array (Array), function (Function).

Tip: Symbol is a new data type introduced in ECMAScript6 that represents a unique value.

1) String type

A string (String) type is a piece of text wrapped in single or double quotes, such as' 123', "abc". It is important to note that single and double quotes are different ways to define a string and are not part of a string.

2) Number type

Numeric (Number) types are used to define numeric values. There is no distinction between integers and decimals (floating point numbers) in JavaScript, and Number types are used to represent numeric values.

Note: the values that can be defined by the Number type are not infinite, and the Number type in JavaScript can only represent values between-(2 ∧ 53-1) and (2 ∧ 53-1).

3) Boolean type

There are only two values of Boolean type, true (true) or false (false). They are often used in condition judgment. In addition to directly using true or false to define Boolean variables, you can also get Boolean values through some expressions.

4) Null type

Null is a special data type with only one value, indicating a "null" value, that is, there is no value, nothing, and is used to define a null object pointer.

Using the typeof operator to look at the type of Null, you will find that the type of Null is Object, indicating that Null actually uses a special value that belongs to Object (object). So by assigning the variable to Null, we can create an empty object.

5) Undefined type

Undefined is also a special data type with only one value, indicating that it is undefined. When we declare a variable without assigning a value to it, the default value for that variable is Undefined.

6) Symbol type

Symbol is a new data type introduced in ECMAScript6, which represents a unique value. Values of type Symbol need to be generated using the Symbol () function.

7) Array type

An Array is a collection of data arranged in order, each value in the array is called an element, and the array can contain any type of data. Defining an array in JavaScript requires square brackets [], and each element in the array is separated by a comma, for example:

[1,2,3, 'hello', true, null]

Alternatively, you can use the Array () function to create an array, as shown in the following example:

Var arr = new Array (1,2,3,4); console.log (arr); / / output [1,2,3,4]

8) Function type

A function (Function) is a block of code with specific functions. The function does not run automatically, but needs to be called through the function name, as shown in the following example:

Function sayHello (name) {return "Hello," + name;} var res = sayHello ("Peter"); console.log (res); / / output Hello, Peter

In addition, functions can be stored in variables, objects, arrays, and functions can be passed as arguments to or returned from other functions.

9) Object type

The Object type in JavaScript is an unordered set of keys and values. Curly braces {} are required to define the object type. The syntax format is as follows:

{name1: value1, name2: value2, name3: value3,..., nameN: valueN}

Name1, name2, name3,..., and nameN are the keys in the object, and value1, value2, value3,..., and valueN are the corresponding values.

In JavaScript, the keys of the object type are of string type, and the value can be of any data type. To get a value in an object, you can use the object name. The form of the key.

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