const o = {
'a': 1,
'b': 2,
'あ b': 3,
};
const key = 'あ b';
const l = 100000;
console.time();
for (let i = 0; i < l; i += 1) {
key in o;
}
console.timeEnd();
console.time();
for (let i = 0; i < l; i += 1) {
o.hasOwnProperty(key);
}
console.timeEnd();
//undefined: 5.921ms
//undefined: 9.741ms
