How to manipulate js arrays quickly and efficiently?

the array operation of js has always been a headache for me. In the past, dealing with arrays is a variety of foreach nesting, filter,map. After writing, I always feel that there will be some optimization, but I really don"t know how to optimize it because of my limited ability. The code is as follows:

let arr = [{
        id: 10,
        name: "IOS",
        status: false
    }, {
        id: 11,
        name: "Android",
        status: false
    },
    {
        id: 12,
        name: "",
        status: false
    },
    {
        id: 13,
        name: "",
        status: false
    },
    {
        id: 20,
        name: "PC",
        status: true
    }]
    // statustrueid
    
    let arr2 = arr.filter(item => item.status)
    let arr3 = arr2.map(item => item.id)
    let str = arr3.join(",")

ask all the bosses for advice.

Array-method jav

Dec.24,2021

semantically, it is more recommended to use your way of writing, which is simple and intuitive. In fact, your writing method can be simplified to

 let str = arr.filter(item => item.status).map(item => item.id).join(',');

however, this method of writing has been cycled twice. In pursuit of efficiency, you can try to change the following method of writing only once in a loop, but the code is difficult to understand

let str = arr.reduce((_arr, item) => item.status && _arr.push(item.id) ? _arr : _arr, []).join(',');

if you optimize manually, you can merge the loop.
you can also rely on the lazy evaluation feature of lodash to let lodash optimize it automatically

let str=_.chain(arr).filter('status').map('id').join(',').value()

let arr = [];
for (let i = 1; i < 10000000; iPP) {
    arr.push({id: i, status: Math.random() > 0.5});
}

console.time('time1');
let arr2 = arr.filter(item => item.status);
let arr3 = arr2.map(item => item.id);
var str = arr3.join(',');
console.timeEnd('time1');

const _ = require('lodash');
const calculateChain = _.chain(arr).filter('status').map('id').join(',');
console.time('time2');
var str = calculateChain.value();
console.timeEnd('time2');

console.time('time3');
var str = arr.reduce((_arr, item) => item.status && _arr.push(item.id) ? _arr : _arr, []).join(',');
console.timeEnd('time3');

it is the fastest to use lodash in actual measurement. It should be that join is also an o (n) operation, and there is room for optimization

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