constructor Property (JavaScript)

Specifies the function that creates an object.


The required object is the name of an object or function.

The constructor property is a member of the prototype of every object that has a prototype. This includes all intrinsic JavaScript objects except the Global and Math objects. The constructor property contains a reference to the function that constructs instances of that particular object.

The following example illustrates the use of the constructor property.

function testObject(ob)
    if (ob.constructor == String)
        return ("Object is a String.");
    else if (ob.constructor == MyFunc)
        return ("Object is constructed from MyFunc.");
        return ("Object is neither a String nor constructed from MyFunc.");

// A constructor function.
function MyFunc() {
    // Body of function.

var x = new String("Hi");
document.write ("<br />");

var y = new MyFunc;

The output of this program is as follows.

Object is a String.
Object is constructed from MyFunc.

Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards. See Version Information.

Applies To: Array Object (JavaScript)| Boolean Object (JavaScript)| Date Object (JavaScript)| Function Object (JavaScript)| Math Object (JavaScript)| Number Object (JavaScript)| Object Object (JavaScript)| String Object (JavaScript)