javascript - 将属性附加到图例的有效方法

Question

我正在开发一个应用程序 - 它将循环数据 - 我想将一个属性附加到现有图例 - 不使用两个 for 循环。

let listRegions = [{
    "label" : "A",
    "value" : "SIEA"
},{
    "label" : "E",
    "value" : "SIEE"
},{
    "label" : "JA",
    "value" : "SIEJA-JAPAN"
},{
    "label" : "AS",
    "value" : "SIEJA-ASIA"
}];

本质上 - 当它遇到一行数据时 - 我想克隆这个数组 - 并将 isInincluded 属性添加到每个值 - 但如果找到，则将 isInincluded 设置为 true

let newList= [{
    "label" : "A",
    "value" : "SIEA",
    "isIncluded": true
},{
    "label" : "E",
    "value" : "SIEE",
    "isIncluded": false
},{
    "label" : "JA",
    "value" : "SIEJA-JAPAN",
    "isIncluded": false
},{
    "label" : "AS",
    "value" : "SIEJA-ASIA",
    "isIncluded": false
}];

<小时/>

类似这样的东西 https://jsfiddle.net/eb2zx70m/1/

let listRegions = [{
  "label": "A",
  "value": "SIEA"
}, {
  "label": "E",
  "value": "SIEE"
}, {
  "label": "JA",
  "value": "SIEJA-JAPAN"
}, {
  "label": "AS",
  "value": "SIEJA-ASIA"
}];

console.log("listRegions", listRegions);

var regions = ["SIEJA-ASIA", "SIEE"];
console.log("regions", regions);

for (var i = 0; i < regions.length; i++) {


  let legendRegions = [];
  listRegions.forEach(function(e) {
    console.log("regions[i]", regions[i]);
    console.log("e.value", e.value);

    if (e.value === regions[i]) {
      console.log("e.value", e.value);
      e.enabled = true;
    } else {
      e.enabled = false;
    }
    legendRegions.push(e);

    console.log("newList", legendRegions);
  });



};

Answer 1

试试这个:

// N list regions
const listRegions = [{
  "label": "A",
  "value": "SIEA"
}, {
  "label": "E",
  "value": "SIEE"
}, {
  "label": "JA",
  "value": "SIEJA-JAPAN"
}, {
  "label": "AS",
  "value": "SIEJA-ASIA"
}];

// K regions
const regions = ["SIEJA-ASIA", "SIEE"];
// complexity O(K)
const includedRegions = regions.reduce((res, region) => ({
  ...res,
  [region]: true
}), {});

// complexity O(N)
const newList = listRegions.map(region => ({
  ...region,
  isIncluded: !!includedRegions[region.value]
}));

// total complexity O(N + K)
console.log(newList);

这里是相同的解决方案，但没有声明额外的 regionsInincluded map 。该映射作为 thisArg 传递到 Array.map()功能:

// N list regions
const listRegions = [{
  "label": "A",
  "value": "SIEA"
}, {
  "label": "E",
  "value": "SIEE"
}, {
  "label": "JA",
  "value": "SIEJA-JAPAN"
}, {
  "label": "AS",
  "value": "SIEJA-ASIA"
}];

// K regions
const regions = ["SIEJA-ASIA", "SIEE"];

// complexity O(N) and O(K) for thisArg value
const newList = listRegions.map(region => ({
  ...region,
  isIncluded: Boolean(this[region.value])
}), regions.reduce((res, region) => ({
  ...res,
  [region]: true
}), {}));

// total complexity O(N + K)
console.log(newList);