Example from here
Creating constructors
To write your own constructors, you use the this keyword within the constructor to refer to the newly-created object. The constructor initializes the object.
In the example below:
The make7Table constructor creates a multiplication table for number 7 The size property is introduced to keep track of the number of elements The value of each element is initialized
function make7Table(numElements)
{
this.size = numElements;
var cnt;
for(cnt = 0; cnt < numElements; cnt++)
{
this[cnt] = cnt*7;
}
}
// Use the constructor to create and initialize an array.
myArray = new make7Table(10);
document.write(myArray[5]);
document.write("This table has " + myArray.size + " elements");
To run the code, paste it into JavaScript Editor, and click the Execute button. myArray[5] retrieves the element with the value of 5*7 = 35.