ES2015のMap,Setで重複カット
2020-06-29
Set,Mapを使うことで今までごにょごにょしてた部分がスッキリ書けるようになる
Set
const allNames = ['a','b','c','c','d','b','a'];
const names = [...new Set(allNames)];
// ['a','b','c','d']Map
const uniq = new Map();
const users = [
{id: 'aaa', name: 'hoge'},
{id: 'aaa', name: 'hoge'},
{id: 'bbb', name: 'fuga'},
]
for (let u of users) {
uniq.set(u['id'], u)
}
console.log(uniq.values());
// { id: 'aaa', name: 'hoge' },
// { id: 'bbb', name: 'fuga' },
console.log(uniq.entries());
// [Map Entries] {
// [ 'aaa', { id: 'aaa', name: 'hoge' } ],
// [ 'bbb', { id: 'bbb', name: 'fuga' } ]
// }
console.log(uniq.size); // 2あまり観測範囲で使っているの見ないが便利なので使っていきたい
