集合与地图类型

// 集合类型
let actions = new Set();

actions.add('read')
actions.add('write').add('update')
actions.add('delete')

console.log(actions); // Set(4) { "read", "write", "update", "delete" }

actions.add('read').add('read').add('delete').add('write').add('update')

console.log(actions) // { "read", "write", "update", "delete" }

console.log(actions.entries()); // SetIterator {"read" => "read", "update" => "update", "delete" => "delete"}
console.log(actions.keys()); // Set Iterator {  }
console.log(actions.values()); // Set Iterator {  }

for(let element of actions) {
    console.log(element); // "read", "write", "update", "delete"
}

console.log(actions.size); // 4

console.log(actions.has('hide')); // false

console.log(actions.has('write')); // true

let items = new Map();

items.set('slipper', 50);
items.set('shoes', 200);
items.set('pants', 100).set('shift', 150);

console.log(items); // { slipper → 50, shoes → 200, pants → 100, shift → 150 }

console.log(items.size); // 4

console.log(items.entries()); // Map Iterator {  }
console.log(items.keys()); // Map Iterator {  }
console.log(items.values()); // Map Iterator {  }

for(let [ product, price ] of items) {
    console.log(`One ${product} costs ${price}.`)
}

/*

    One slipper costs 50.
    One shoes costs 200.
    One pants costs 100.
    One shift costs 150.

*/