What is the point of the 'Symbol' type in ECMA-262-v6?

Question

What is the point of the \'Symbol\' type in ECMA-262-v6? Fast path implementation for object keys? What does it do under the hood - hash it with the guarantee that the under

Answer 1

They pretty much help us having naming collisions. Anytime that you want to create a property in a unique way, that's when you should reach for a symbol.

Take a look at my example

const bert = Symbol('Bert');

'Bert'

Note: this is not a value this is what they called a descriptor, because the symbol itself is just a unique identifier. So if you were to visualize what a symbol would be maybe you can visualize is as something like this "sdfasdfa2342134987fgsdfgsdf9808fsfgsd" absolute unique symbol so that you can make sure that it will never overrides any other piece of code in there.

What's cool about this is if I create a second symbol, like

const person = Symbol('Bert')

You can see I used 'Bert' again. Are those going to be the same because I described them as the same thing?

const bert = Symbol('Bert');
const person = Symbol('Bert');


console.log(bert);
console.log(person);
console.log(bert === person);
console.log(bert == person);

This can be useful if you were creating an object of your class.

  const classRoom = {
    'Mia' : { grade: 50, gender: 'female' },
    'Gilbert': { grade: 80, gender: 'male' },
    'Gilbert' { grade: 80, gender: 'male' },
  };

But then you have another named Gilbert, so you got a naming collision there. So imagine if you're working on million and millions of data. So rather than using the persons name or using some sort of unique identifier we can use a symbol to name them.

  const classRoom = {
    [Symbol('Mia')] : { grade: 50, gender: 'female' },
    [Symbol('Gilbert')]: { grade: 80, gender: 'male' },
    [Symbol('Gilbert')]: { grade: 80, gender: 'male' },
  };

Another thing about symbols is that they are not enumerable, which means we cannot loop over them if I were to do

  for (const person in classRoom) {
    console.log(person);
  }

I get nothing.

If you do want to get access to all your symbols because theyres some information that you want to get you can use the object method.

  const syms = Object.getOwnPropertySymbols(classRoom);
  const data = syms.map(sym => classRoom[sym]);
  console.log(data);