A JavaScript Quirk

#programming #javascript

It’s common knowledge that JavaScript has its fair share of quirks. But this is one I find particularly interesting. (0, fn)() acts as a way to unbind this and execute a function without a context. This is because fn is now being treated as an lvalue.

class Test {
  constructor() {
    this.member = "I EXIST";
  }

  logThis() {
    console.log("Logging:", this);
  }
}

const instance = new Test();
instance.logThis();
// Logging: Test {member: 'I EXIST'}

(0, instance.logThis)();
// Logging: undefined

In the example above, it’s equivalent to calling the logThis method using instance.logThis.bind(undefined)().