JS merge multiple objects and remove duplicates

Method 1 :

let o1 = { a: 1, b: 2 };
let o2 = { c: 4, d: 5 };
let o3 = {...o1, ...o2};//{ a: 1, b: 2, c: 4, d: 5}

If there are duplicates key, Then the following will overwrite the previous value

let o1 = { a: 1, b: 2 };
let o2 = { c: 4, b: 5 };
let o3 = {...o1, ...o2};//{ a: 1, b: 5, c: 4}

Method 2 ：

Object.assign Method is used for merging objects , Put the source object （source） All enumerable properties of , Copy to target object （target）.

const target = { a: 1 };

const source1 = { b: 2 };
const source2 = { c: 3 };

Object.assign(target, source1, source2);
target // {a:1, b:2, c:3}

Object.assign The first parameter of the method is the target object , Later parameters are all source objects .

Be careful , If the target object has the same property as the source object , Or multiple source objects have properties with the same name , Then the following properties will overwrite the previous properties .

const target = { a: 1, b: 1 };

const source1 = { b: 2, c: 2 };
const source2 = { c: 3 };

Object.assign(target, source1, source2);
target // {a:1, b:2, c:3}