4 types of recognition methods in JavaScript _javascript tips

The specific contents are as follows:

1.typeof

String form for "output" first letter lowercase

function

[A] can recognize the standard type (recognize null as Object)
[b] does not recognize specific object types (except for function)

Instance

Console.log (typeof "Jerry");/"string"
Console.log (typeof);//"Number"
Console.log (typeof true);/" Boolean "
Console.log (typeof undefined);//" Undefined "
Console.log (typeof null);//" Object "
Console.log (typeof {Name: "Jerry"});/"Object"
Console.log (typeof function () {});//"function"
Console.log (typeof []); /"Object"
Console.log (typeof new Date);//"Object"
Console.log (typeof/\d/);//"Object"
function Person () {};
Console.log (typeof new person);//"Object"

2.object.prototype.tostring

string form of output [object data type]

function

[A] can recognize standard types and built-in object types
[b] does not recognize custom types

"Construct Method"

function type (obj) {return
Object.prototype.toString.call (obj). Slice (8,-1). toLowerCase ();
}  

"Instance 1"

Console.log (Object.prototype.toString.call ("Jerry"));//[object String]
console.log ( Object.prototype.toString.call ())//[object number]
Console.log (Object.prototype.toString.call (true));//[ Object Boolean]
console.log (Object.prototype.toString.call (undefined));//[object undefined]
console.log ( Object.prototype.toString.call (null));//[object null]
Console.log (Object.prototype.toString.call ({name:) Jerry "}));//[object Object]
console.log (Object.prototype.toString.call (function () {}));//[object Function]
Console.log (Object.prototype.toString.call ([]));//[object Array]
console.log ( Object.prototype.toString.call (new date);//[object Date]
console.log (Object.prototype.toString.call (/\d/)) ;//[object RegExp]
function person () {};
Console.log (Object.prototype.toString.call (new person));//[object Object]

"Instance 2"

function type (obj) {return
  Object.prototype.toString.call (obj). Slice (8,-1). toLowerCase ();
}
Console.log (Type ("Jerry"));//"string"
console.log (type);/"Number"
Console.log (Type (true)); Boolean
console.log (type (undefined));//"Undefined"
console.log (Type (null));//"NULL"
Console.log ( Type ({name: "Jerry"}));//"Object"
console.log (Type (function () {})),//"function"
console.log (Type ([])); /' array '
console.log (new Date);//"Date"
console.log (Type (/\d/)),//"regexp"
function person ( ){};
Console.log (type (new person));//"Object"

3.constructor

Output function data type () {[native code]} or function custom type () {}

function

[A] can recognize standard types, built-in object types, and custom types
[b] cannot recognize undefined, NULL, error

"Construct Method"

function type (obj) {
  var temp = obj.constructor.toString ();
  Return Temp.replace (/^function (\w+) \ (\). +$/, ' $ ';
}

"Instance 1"

Console.log (("Jerry"). constructor);//function String () {[native code]}
Console.log ((). constructor);// function number () {[native code]}
Console.log ((true) constructor);//function Boolean () {native code]}
// Console.log ((undefined). constructor);//Error
//console.log ((null). constructor);//Error
Console.log ({name: " Jerry "}). constructor);//function Object () {[native code]}
Console.log ((function () {}). constructor);//function Function () {[native code]}
Console.log (([]). constructor);//function Array () {[native code]}
Console.log ( New date). Constructor//function Date () {[native code]}
Console.log ((/\d/). constructor);//function RegExp () { Native code]}
function person () {};
Console.log (new person). constructor);//function person () {}

"Instance 2"

function type (obj) {
  var temp = obj.constructor.toString (). toLowerCase ();
  Return Temp.replace (/^function (\w+) \ (\). +$/, ' $ ';
}
Console.log (Type ("Jerry"));//"string"
console.log (type);/"Number"
Console.log (Type (true)); Boolean '
//console.log (type (undefined));//Error
//console.log (type (null));//Error
Console.log (type ({name : "Jerry"});//"Object"
console.log (Type (function () {}))//"function"
console.log (Type ([]));//"Array"
Console.log (new date);//"Date"
console.log (Type (/\d/));//"regexp"
function person () {};
Console.log (type (new person));//"Person"

4.instanceof

' Output ' true or false

function

[A] can recognize built-in object types, custom types, and their parent types
[b] does not recognize the standard type and returns false
[C] cannot recognize undefined, NULL, error

Instance

Console.log ("Jerry" instanceof String);//false
Console.log (instanceof number);//false
Console.log (True instanceof Boolean);//false
//console.log (undefined instanceof undefined);//error
//console.log (null instanceof Null);//Error
Console.log ({name: "Jerry"} instanceof Object);//true
Console.log (function () {} instanceof Function);//true
Console.log ([] instanceof Array);//true
Console.log (new date instanceof date); True
Console.log (/\d/instanceof RegExp);//true
function Person () {};
Console.log (new person instanceof person),//true
console.log (new person instanceof Object);//true

The above is a detailed description of JavaScript in 4 types of identification methods, I hope you like.