How to accurately determine the data type of a variable in js

can be achieved through the toString() method.

(Recommended tutorial: js tutorial)

Function introduction:

toString() is the prototype method of Object. When this method is called, the current value is returned by default [[Class]] of the object. This is an internal property with the format [object Xxx] , where Xxx is the type of object.

For Object objects, calling toString() directly will return [object Object]. For other objects, you need to call / apply to return the correct type information.

Function syntax:

number.toString(radix)

Code example:

Object.prototype.toString.call('') ;   // [object String]
Object.prototype.toString.call(1) ;    // [object Number]
Object.prototype.toString.call(true) ; // [object Boolean]
Object.prototype.toString.call(Symbol()); //[object Symbol]
Object.prototype.toString.call(undefined) ; // [object Undefined]
Object.prototype.toString.call(null) ; // [object Null]
Object.prototype.toString.call(new Function()) ; // [object Function]
Object.prototype.toString.call(new Date()) ; // [object Date]
Object.prototype.toString.call([]) ; // [object Array]
Object.prototype.toString.call(new RegExp()) ; // [object RegExp]
Object.prototype.toString.call(new Error()) ; // [object Error]
Object.prototype.toString.call(document) ; // [object HTMLDocument]
Object.prototype.toString.call(window) ; //[object global] window 是全局对象 global 的引用

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