js array object deduplication

Today, I will introduce three methods for deduplication of array objects, which are simple and convenient.
There is such a group of array objects:

let arr = [{id: '1',key: '1',value: 'Moon'}, {id: '3',key: '2',value: 'Kexin'}, {id: '2',key: '3',value: 'Little Red'}, {id: '1',key: '1',value: 'Xiaoxin'}, {id: '1',key: '2',value: 'Xiaojing'}]

1. Methods for accessing properties of objects

let newArr = [];let obj = {};for (var i = 0; i < arr.length; i++) {if (!obj[arr[i].key]) {newArr.push(arr[i])obj[arr[i].key] = true}}console.log(newArr);

2, Map() method

set method sets the key value corresponding to the key, and then returns the entire Map structure.If the key already has a value, the key value will be updated, otherwise the key will be newly generated.

The values ​​method can return a traverser object of the Map object's values

let map = new Map();for (let item of this.arr) {map.set(item.id, item);}this.arr = [...map.values()];console.log(this.arr)

3, reduce() method

reduce() method receives a function as an accumulator, and each value in the array (from left to right) starts to reduce, and finally calculates to a value
array.reduce(function(total, currentValue, currentIndex, arr), initialValue)

Parameters

Description

total

Required.The initial value, or the return value after the calculation ends.

currentValue

Required.current element

currentIndex

Optional.the index of the current element

arr

Optional.The array object to which the current element belongs.

initialValue

Optional.The initial value passed to the function

const obj = {}arr = arr.reduce((total, next) => {obj[next.key] ? '' : obj[next.key] = true && total.push(next)return total}, [])console.log(arr)

There is another requirement here. If there are two or more judgment conditions, de-duplicate the array object and add a judgment condition.

const hasObj = {}arr = arr.reduce((total, next) => {const filterKey = next.key + next.id;hasObj[filterKey] ? "" : hasObj[filterKey] = true && total.push(next)return total}, [])console.log(arr)

Hope this helps you!

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