This is an alternative way to deliver a string version of a number value. In this case, it is formatted as a Number literal and can then be used in an eval() function to assign another number.
If you run the example below, it should yield this as a result:
The result of calling this method is a string version of the number formatted as a Number literal.
// Create a number and then examine its source myNumber = new Number(1000); document.write(myNumber.toSource());