If the concept of a set still hasn't set in, let's take an example with brunch, because everyone absolutely loves brunch. Let's say it's a busy Sunday morning at a restaurant and people are coming in for brunch and they want to put their name on the list.
const brunch = new Set();
// as people start coming in
brunch.add('Wes');
brunch.add('Sarah');
brunch.add('Simone');We've created a variable called brunch, which is a new set. Then as people start coming in, we're adding them to the list.
Then we are ready to open. What we're going to do is take the values from our const brunch and start to use it.
const brunch = new Set();
// as people start coming in
brunch.add('Wes');
brunch.add('Sarah');
brunch.add('Simone');
// ready to open
const line = brunch.values();Now, we're working with line and we could say, "All right, who's up?"
const brunch = new Set();
// as people start coming in
brunch.add('Wes');
brunch.add('Sarah');
brunch.add('Simone');
// ready to open
const line = brunch.values();
console.log(line.next().value);We're going to use the console to see line.next().value because line.next() is going to give us the generator item, and .value is going to be the actual item from our set.
Over in the console, you'll see that Wes is up. Then if we've got room for another person, we'll just call that same code again:
const brunch = new Set();
// as people start coming in
brunch.add('Wes');
brunch.add('Sarah');
brunch.add('Simone');
// ready to open
const line = brunch.values();
console.log(line.next().value);
console.log(line.next().value);And you'll see in the console that Sarah is up.
If you call brunch in the console, you'll see that Wes, Sarah, and Simone are still in the brunch set.
If you call line, Just Simone is actually left.
That's really interesting because when you call next() against line, it will remove itself from the SetIterator you can see in the console when you call line. However, the set, brunch, is sort of the gold list of everyone that has currently went through it.
Then people start showing up. We've seated our first couple customers and people are showing up, so we can just starting adding them to the initial set using brunch.add, then using line.next().value to iterate over the set.
const brunch = new Set();
// as people start coming in
brunch.add('Wes');
brunch.add('Sarah');
brunch.add('Simone');
// ready to open
const line = brunch.values();
console.log(line.next().value);
console.log(line.next().value);
brunch.add('Heather');
brunch.add('Snickers');
console.log(line.next().value);
console.log(line.next().value);
console.log(line.next().value);Notice how we're not adding them to line, we're adding them to the initial set brunch.
We can just keep calling next() on it. We can call it next a few times, and as we do that, people are being seated: Wes, Sarah, Simone, Heather, Snickers.
Even though I added these after creating brunch, which is our set, and creating line, we can still add people to the original set, and the iterator is still going to iterate on through to them.