Function: prototype

The prototype data property of a Function instance is used when the function is used as a constructor with the new operator. It will become the new object’s prototype.

Note: Not all Function objects have the prototype property — see description.

When a function is called with new, the constructor’s prototype property will become the resulting object’s prototype.

You can read Inheritance and the prototype chain for more information about the interactions between a constructor function’s prototype property and the resulting object’s prototype.

A function having a prototype property is not sufficient for it to be eligible as a constructor. Generator functions have a prototype property, but cannot be called with new: