# JavaScript - Map vs Object
###### tags: `Javascript`

==比較Map與Object 操作上效能差異==

### 建置100萬筆資料

const standard = BigInt(1000000);
const testmap = new Map()
const obj = {}

const setMap = process.hrtime.bigint();
for (let i = 0; i < 1000000; i++){
    testmap.set(`key${i}`,`test ${i}`);
}
const EndsetMap = process.hrtime.bigint();

const setObj = process.hrtime.bigint();
for (let i = 0; i < 1000000; i++){
    obj[`key${i}`] = `test ${i}`;
}
const endsetObj = process.hrtime.bigint();

>Map **寫入資料**,優於Object
---
### 連續取得單筆資料(10萬筆)

const getMap = process.hrtime.bigint();
const value = testmap.get(`key1000`);
const endgetMap = process.hrtime.bigint();

const getObj = process.hrtime.bigint();
const value2 = obj[`key1000`]
const endgetObj = process.hrtime.bigint();

> Object **取得單筆資料**,優於Map
---

### 轉換成Array(100萬筆)

const MapLoopStart = process.hrtime.bigint();
const data = [...testmap.keys()];
const MapLoopEND = process.hrtime.bigint();

const ArrayStart = process.hrtime.bigint();
const data2 = Array.from(testmap.keys());
const ArrayEND = process.hrtime.bigint();

const ObjLoopStart = process.hrtime.bigint();
const data3 = Object.keys(obj)
const ObjLoopEND = process.hrtime.bigint();

>Map **轉換到一般Array**,優於Object(==明顯!!==)

### 結論
> * 在單筆查詢速度, Object 略優於 Map
>
> * 在操作上Array提供許多方便的函式,時常會將Object轉換為Array進行操作
> 轉換成Array的過程, Map本身是可疊代的,效能上明顯優於Object,
> 當需要儲存大量key-value pair資料操作時, Map是相當不錯的選擇!!