Four ways to deduplicate array objects (strongly push the last one!!!)

Hello, hello, here I come again.

What I share today is the way to deduplicate array objects. Let’s first look at the form of array objects:

let arrObj = [
    { name: "小红", id: 1 },
    { name: "小橙", id: 1 },
    { name: "小黄", id: 4 },
    { name: "小绿", id: 3 },
    { name: "小青", id: 1 },
    { name: "小蓝", id: 4 }
];

The following is the result I want to get, which is to delete the objects with the same value of id

Method 1: Double for loop

Two-by-two comparison, if the id value of the latter object is equal to the id value of the previous object, delete the latter object

let arrObj = [
    { name: "小红", id: 1 },
    { name: "小橙", id: 1 },
    { name: "小黄", id: 4 },
    { name: "小绿", id: 3 },
    { name: "小青", id: 1 },
    { name: "小蓝", id: 4 }
];
function fn1(tempArr) {
    for (let i = 0; i < tempArr.length; i++) {
        for (let j = i + 1; j < tempArr.length; j++) {
            if (tempArr[i].id == tempArr[j].id) {
                tempArr.splice(j, 1);
                j--;
            };
        };
    };
    return tempArr;
};
console.log(fn1(arrObj));

 Method 2: indexOf()

Define an array to store the value of id, and then compare them one by one, and delete the objects with duplicate id values

let arrObj = [
    { name: "小红", id: 1 },
    { name: "小橙", id: 1 },
    { name: "小黄", id: 4 },
    { name: "小绿", id: 3 },
    { name: "小青", id: 1 },
    { name: "小蓝", id: 4 }
];
function fn2(tempArr) {
    let newArr = [];
    for (let i = 0; i < tempArr.length; i++) {
        if (newArr.indexOf(tempArr[i].id) == -1) {
            newArr.push(tempArr[i].id);
        } else {
            tempArr.splice(i, 1);
            i--;
        };
    };
    return tempArr;
};
console.log(fn2(arrObj));

Method 3: The method of object access property

Use the method of object access attribute to determine whether the attribute value exists

let arrObj = [
    { name: "小红", id: 1 },
    { name: "小橙", id: 1 },
    { name: "小黄", id: 4 },
    { name: "小绿", id: 3 },
    { name: "小青", id: 1 },
    { name: "小蓝", id: 4 }
];
function fn3(tempArr) {
    let result = [];
    let obj = {};
    for (let i = 0; i < tempArr.length; i++) {
        if (!obj[tempArr[i].id]) {
            result.push(tempArr[i]);
            obj[tempArr[i].id] = true;
        };
    };
    return result;
};
console.log(fn3(arrObj));

Method 4: Map()

The has method can determine whether the specified element exists in the Map object, and return true if there is, otherwise return false

The set method can add new elements to the Map object map.set(key, value)

The values ​​method can return the traverser object of the value of the Map object

let arrObj = [
    { name: "小红", id: 1 },
    { name: "小橙", id: 1 },
    { name: "小黄", id: 4 },
    { name: "小绿", id: 3 },
    { name: "小青", id: 1 },
    { name: "小蓝", id: 4 }
];
// 方法一：
let map = new Map();
for (let item of arrObj) {
    if (!map.has(item.id)) {
        map.set(item.id, item);
    };
};
arr = [...map.values()];
console.log(arr);



// 方法二： (代码较为简洁)
const map = new Map();
const newArr = arrObj.filter(v => !map.has(v.id) && map.set(v.id, v));
// const newArr = [...new Map(arrObj.map((v) => [v.id, item])).values()];
console.log(newArr);

The above four methods can be selected according to your own preferences. If you make any mistakes, please correct me.