Question

我想将一个数组的元素插入另一个数组。我有两个名为a和b的数组，我想从数组a中获取订单数量并将其插入到数组b的对象中：这是数组

var a = [{
  "order_id": "241918",
  "product_id": "152737",
  "order_qty": "1",
  "customer_note": "Only nappy pants subsitutes please",
  "out_of_stock": "find_best_match",
  "cust_sub_prod_id": null,
  "cust_sub_prod_qty": null
}]

 var b = [{
  "id": "282",
  "product_id": "152737",
  "sku": "b175a9ea5f4d9b4766e74079c2bec8",
  "prod_name": "PnP Baby Marrows 1kg",
  "image_url": "https://www.onecart.co.za/wp-content/uploads/2017/11/108890_EA.jpg",
  "vendor": "Pick n Pay",
  "price": "40.69"
}]

Answer 1

都是包含一个普通对象的一元数组因此，使用b [0]可以访问fisrt和唯一的元素（对象）和.order_qty允许您访问所需的属性。

b[0].order_qty = a[0].order_qty;

Answer 2

我不确定这样做是否正确，但是您可以使用var mysql = require("mysql"); var httpSyncRequest = require('sync-request'); var MysqlDatabase = mysql.createConnection({ host: "localhost", user: "root", password: "", database: "myDB" }); MysqlDatabase.connect(); setInterval(function () { MysqlDatabase.query("SELECT 1", function (err, row) { }); }, 3000); MysqlDatabase.query(`Select * from myTable`,function(err,row){ row.forEach(function (result) { var isOpening= httpSyncRequest("GET", "https://myapi.com?ID="+result.ID ).getBody('utf8'); MysqlDatabase.query(`UPDATE myTable SET IsOpening =? WHERE myTable.ID= ?`,[isOpening,result.ID],function(){}); }); });来实现与数据相同的代码，如下所示：

const path = require('path');
const webpack = require('webpack');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const VueLoaderPlugin = require('vue-loader/lib/plugin');
const devMode = process.env.NODE_ENV === 'development';

module.exports = {
    entry: {
        vendor1: ['vendor1', 'vendor2', 'vendor 3'], // all other vendor lists, package.json dependencies 
        vendor2: ['vue'],
        app: './assets/src/app.js'
    },
    resolve: {
        alias: {
            '~': path.resolve(__dirname, 'assets/src')
        }
    },
    module: {
        rules: [
            {
                test: /\.vue$/,
                loader: 'vue-loader'
            },
            {
                test: /\.scss$/,
                use: [
                    {
                        loader: MiniCssExtractPlugin.loader
                    },
                    'css-loader',
                    'postcss-loader',
                    'sass-loader'
                ]
            },
            {
                test: /\.css$/,
                use: ['vue-style-loader', 'css-loader']
            },
            {
                test: /\.(woff2?|ttf|eot|svg)$/,
                use: ['url-loader']
            }
        ]
    },
    optimization: {
        runtimeChunk: 'single',
        splitChunks: {
            cacheGroups: {
                vendor1: {
                    name: 'vendor1',
                    test: 'vendor1',
                    enforce: true
                },
                vendor2: {
                    name: 'vendor2',
                    test: 'vendor2',
                    enforce: true
                }
            }
        }
    },
    externals: {
        jquery: 'jQuery'
    },
    plugins: [new VueLoaderPlugin()]
};

Answer 3

如果您不关心性能

1。如果不确定数组B是否具有与product_id匹配的对象

a.forEach((from)=>{
    //search is there any matching object in array B
    let to = b.find(searching=>from.product_id === searching.product_id);
    if(to!=null){
       to.order_qty = from.order_qty
    }
});

2。如果您确定数组B具有与product_id匹配的对象

a.forEach((from)=>b.find(searching=>from.product_id === searching.product_id).order_qty = from.order_qty);

如果您的阵列大小会很大并且您关心性能：

哦，看来您最好使用其他数据结构而不是数组来存储数据。

好吧，为什么？

Array.prototype.find()的复杂度为O（n），这意味着当数组的长度为1000时，最坏的情况将导致数组内部的find()循环1000次。

当数组A和B都具有n个对象时，使用上述解决方案将使数组B循环n ^ 2次。

当n = 100时，需要搜索10000次
当n = 1000时，需要搜索1000000次
当n = 10000时，需要搜索100000000次

如何解决？

大多数JavaScript引擎使用哈希表实现Map，因此Map.prototype.get()的复杂度为O（1），无论您的Map有1k，10k，100k个对象，都使用其键搜索对象只需要1次。

//Creating data
let a = new Map();
let b = new Map();

a.set("152737",{
  "order_id": "241918",
  "product_id": "152737",
  "order_qty": "1",
  "customer_note": "Only nappy pants subsitutes please",
  "out_of_stock": "find_best_match",
  "cust_sub_prod_id": null,
  "cust_sub_prod_qty": null
});

b.set("152737",{
  "id": "282",
  "product_id": "152737",
  "sku": "b175a9ea5f4d9b4766e74079c2bec8",
  "prod_name": "PnP Baby Marrows 1kg",
  "image_url": "https://www.onecart.co.za/wp-content/uploads/2017/11/108890_EA.jpg",
  "vendor": "Pick n Pay",
  "price": "40.69"
})


//Search and insert data
a.forEach(from =>{
    if(b.has(from.product_id)){
        b.get(from.product_id).order_qty = from.order_qty
    }
})

如何将数组中的对象的属性复制到另一个数组中的另一个对象？

3 个答案:

如果您不关心性能

如果您的阵列大小会很大并且您关心性能：