JavaScript Object Constructor Property

Overview

Returns a pointer to a function reference that created the object's prototype. Note that the value of this property is the function itself, not a string that contains the name of the function. For raw values (such as 1, true or " test "), the property is read-only.

Describe

All objects inherit a property from its prototype constructor :

var New // or o = {}o.constructor = = Objectvarnew Array  //  or a = [] A.constructor = = Arrayvarnew number (3 = = number

Even though some DOM objects are not generated by constructors, you can still compare them with the corresponding constructors. Like what:

Document.constructor == = = Form;

Example 1: Print out a constructor for an object

The following example first creates an object that constructs a prototype (that is, a constructor) Tree  and a prototype theTree . The properties of the object are then printed out theTree  constructor  .

function Tree (name) {   this. Name = name;}  var New Tree ("Redwood""Thetree.constructor is" + thetree.constructor);

Print output:

function Tree (name) {    this. Name = name;} 

Example 2: Changing the value of the constructor property of this object

The following example shows how to modify the value of the constructor property of a primitive type object. Only true, 1 and "test" are not affected, because they are created as read-only native constructors (native constructors). This example also shows that it is not safe to rely on an object's constructor property.

functionType () {};varTypes = [    NewArray, [],NewBoolean,true,//remains unchanged    NewDate,NewError,NewFunction,function() {}, Math,NewNumber ,1,//remains unchanged    NewObject, {},NewRegExp,/(?:) /,    NewString,"Test"//remains unchanged]; for(vari = 0; i < types.length; i++) {Types[i].constructor=Type; Types[i]= [Types[i].constructor, types[i]instanceofType, types[i].tostring ()];}; Console.log (Types.join ("\ n"));

Specification

Spec Version	Canonical State	Annotations
ECMAScript 1st Edition. Implemented in JavaScript 1.1	Standard	Initial definition.
ECMAScript 5.1 (ECMA-262) Objectprototype.constructor	Standard
ECMAScript 6 (ECMA-262) Object.prototype.constructor	Draft

Browser compatibility

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic Support	(Yes)	(Yes)	(Yes)	(Yes)	(Yes)

JavaScript Object Constructor Property