JS data type

JS is a lightweight, weak type of scripting language.

The variables in JS are loosely typed and can store any data type: Basic structure: var variable name = value;

such as: Var num=12;　　var str= ' month falls silent ';　　var boo=true; var obj={name: ' Month falls silent '};

var ary=[1,2,3,4];　　var reg=/^[0-9]$/; var fn=function () {};

Data types in JS: basic data types and reference data types

Basic data type: consists of simple data segments, including: Number (numeric), string (String), Boolean (True,false), null (NULL), undefined (undefined)

　　　　

Reference data type: composed of complex data, including object data type, functions (function data type)

Object also contains: Object, Math (mathematical method), string (string method), array (array), REGEXP (Regular), date (Time function)

The principle of reference data type: Define a reference data type, first open a new memory address, and then assign a dummy value to the variable (address, a reference to the newly opened memory space)

such as: obj={name: ' AAA '}

Obj.name= ' BBB '; The new memory space is accessed through the virtual memory address, and the value ' AAA ' of the name attribute in the memory space is changed

Data type detection in JS:

typeof detection data type, returns a string representing the data type

Note: Nan is number type undefined is undefined type

Null is an object type null represents null and is an empty pointer

Objects that are commonly used in TypeOf can only return object and cannot be subdivided into specific

Instanceof is used to detect if an instance belongs to a class.

ToString can subdivide object

Constructor structural function detection

JS data type