Javascript "Not a Constructor" Exception while creating objects
The code as posted in the question cannot generate that error, because Project
is not a user-defined function / valid constructor.
function x(a,b,c){}
new x(1,2,3); // produces no errors
You've probably done something like this:
function Project(a,b,c) {}
Project = {}; // or possibly Project = new Project
new Project(1,2,3); // -> TypeError: Project is not a constructor
Variable declarations using var
are hoisted and thus always evaluated before the rest of the code. So, this can also be causing issues:
function Project(){}
function localTest() {
new Project(1,2,3); // `Project` points to the local variable,
// not the global constructor!
//...some noise, causing you to forget that the `Project` constructor was used
var Project = 1; // Evaluated first
}
An additional cause of this can be ES2015 arrow functions. They cannot be used as constructors.
const f = () => {};
new f(); // This throws "f is not a constructor"
For me it was the differences between import
and require
on ES6.
E.g.
processor.js
class Processor {
}
export default Processor
index.js
const Processor = require('./processor');
const processor = new Processor() //fails with the error
import Processor from './processor'
const processor = new Processor() // succeed