Working with the JavaScript Set Built-in

Working with the built-in JavaScript Set() object.

The Set object lets you store unique values of any type, whether primitive values or object references.

let out;
let setA = new Set([1, 2, 3, 4, 4, 4, 5]);

// Confirm set contains a member.
out = setA.has(5); // true
console.log(out);

// Remove an item from the set.
setA.delete(5);
out = setA.has(5); // false
console.log(out);

// Sets don't allow duplicates, so all those 4s have been
// reduced to a single element.
out = setA.size; // 4
console.log(out);

// Iterate over set members in for loop.
for (let item of setA) console.log(item); // 1, 2, 3, 4

// Add an item to the set.
out = setA.has(6);
console.log(out); // false
setA.add(6);
console.log(out); // true

// Clear all members from the set.
setA.clear();
for (let item of setA) console.log(item); // no output

// A string argument is handled like an array.
let str = 'This is a string';
setA = new Set(str);
out = setA.has('i'); // true
console.log(out);

out = setA.size; // 10
console.log(out);

for (let item of setA) console.log(item); // "T", "h", "i", "s", " ", "a", "t", "r", "n", "g" 
setA.clear();

let o = {
  a: 'red',
  b: 'blue'
};
setA = new Set([o]);
out = setA.has(o); // true
console.log(out);

let o2 = {
  a: 'red',
  b: 'blue'
};
out = setA.has(o2); // false
console.log(out);

o2 = o; // <- change o2 to a reference of o.
out = setA.has(o2); // true
console.log(out);

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