如何从Javascript中的两个不同数组派生新对象值

Question

我有两个数组如下，

var day1 = [{id: 1, type:"20H", cases: 30, fail: 5},
                {id: 1, type:"12C", cases: 10, fail: 3},
                {id: 1, type:"4B", cases: 20, fail: 8}];
              
var day5 = [{id: 5, type:"12C" ,cases: 5, fail: 2},
             {id: 5, type:"4B", cases: 12, fail: 3},
             {id: 5, type:"20H", cases: 20, fail: 6}];

期待下面的数组结果，

var result = [{id: 1, type:"20H", caseCount: 30, failCount: 5, difference: 10, diffPercentage: 50.00},
              {id: 1, type:"12C", caseCount: 10, failCount: 3, difference: 5, diffPercentage: 100.00},
              {id: 1, type:"4B", caseCount: 20, failCount: 8, difference: 8, diffPercentage: 66.66}];

diff和diffPercentage的逻辑如下，

在这里，我不知道如何获取两个数组之间的匹配值并继续。

if(day1.type === day5.type){
    difference = day1.cases - day5.cases;//Here, 30-20 = 10
    diffPercentage = ((day1.cases - day5.cases)/(day5.cases)*100).toFixed(2);// 10/20 * 100 = 50.00
}

尝试了以下，

result = [];

day1.forEach(function(day1Items, idx){
    var day5Items = day5[idx];
    var outputElements = {};
    if(day1Items && day5Items){            
      if(day1Items.type == day5Items.type)){ //Here, I am not getting how to get the matched value between two array and proceed.
        console.log("Inside if block2"); //it is coming here, because, the if condition going index wise check
        outputElements.id = day1Items.id;
        outputElements.type = day1Items.type;
        outputElements.caseCount = day1Items.cases;
        outputElements.failCount = day1Items.fail;
        outputElements.difference = day1Items.cases - day5Items.cases;//Here, I need to get the cases value respective type matched
        outputElements.diffPercentage = ((day1.cases - day5.cases)/(day5.cases)*100).toFixed(2);
        result.push(outputElements);
      }
    }
});

console.log(result);

Answer 1

这应该可行：

 var day1 = [{id: 1, type:"20H", cases: 30, fail: 5},
                    {id: 1, type:"12C", cases: 10, fail: 3},
                    {id: 1, type:"4B", cases: 20, fail: 8}];
              
    var day5 = [{id: 5, type:"12C" ,cases: 5, fail: 2},
                 {id: 5, type:"4B", cases: 12, fail: 3},
                 {id: 5, type:"20H", cases: 20, fail: 6}];
    
        let result = []
        
        day1.forEach(d1 => {
            const day5Item = day5.find(d5 => d5.type === d1.type);
            if(day5Item){
                let difference = d1.cases - day5Item.cases;
                let diffPercentage = (difference/day5Item.cases*100).toFixed(2)
        
                result.push({
                    id:d1.id,type:d1.type,caseCount:d1.cases,failCount:d1.fail,difference,diffPercentage
                })
            }
        });
        
        console.log(result);

Answer 2

您可以使用Map 来实现此目的。

    var day1 = [
          { id: 1, type: "20H", cases: 30, fail: 5 },
          { id: 1, type: "12C", cases: 10, fail: 3 },
          { id: 1, type: "4B", cases: 20, fail: 8 }
     ];

     var day5 = [
          { id: 5, type: "12C", cases: 5, fail: 2 },
          { id: 5, type: "4B", cases: 12, fail: 3 },
          { id: 5, type: "20H", cases: 20, fail: 6 }
     ];


     function merge(arr1, arr2) {
       const hashMap = new Map();
       arr1.forEach((elem) => {
       const elemClone = {
         ...elem,
         failCount: elem.fail,
         caseCount: elem.cases
       };
       delete elemClone.fail;
       delete elemClone.cases;
       hashMap.set(elem.type, elemClone);
     });

     arr2.forEach((elem) => {
       if (hashMap.has(elem.type)) {
         const difference = Math.abs(elem.cases -
           hashMap.get(elem.type).caseCount);
         const diffPercentage = Number(parseFloat((difference / elem.cases) 
           * 100).toFixed(2));
         hashMap.set(elem.type, {
           ...hashMap.get(elem.type),
           difference,
           diffPercentage
          });
        } else {
          hashMap.set(elem.type, elem);
        }
      });

     return Array.from(hashMap.values());
   }

console.log(merge(day1, day5));

Answer 3

这是您的代码的更正版本。

您的代码的问题是，您正在使用 array.forEach 循环遍历 day1 数组，并通过使用 index 从 day5 数组中选择匹配节点。那是磨损的，这仅在数组与类型的顺序相同时才有效。而不是使用var day5Items = day5[idx]; 进行选择，您必须使用Array.find 从第5 天选择节点并检查类型。 Thil 将为您提供所需的节点。

另外计算diffPercentage也有错误

应该是outputElements.diffPercentage = ((day1Items.cases - day5Items.cases)/(day5Items.cases)*100).toFixed(2);，而不是outputElements.diffPercentage = ((day1.cases - day5.cases)/(day5.cases)*100).toFixed(2); 。 day1 和 day5 是数组。您无法访问 day1.cases 或 day5.cases 而应该是 day1Items.cases 和 day5Items.cases

var day1 = [
    { id: 1, type: "20H", cases: 30, fail: 5 },
    { id: 1, type: "12C", cases: 10, fail: 3 },
    { id: 1, type: "4B", cases: 20, fail: 8 }
];

var day5 = [
    { id: 5, type: "12C", cases: 5, fail: 2 },
    { id: 5, type: "4B", cases: 12, fail: 3 },
    { id: 5, type: "20H", cases: 20, fail: 6 },
];
const result = [];

day1.forEach(function(day1Items, idx){
    // You cannot simply select with index.
    // Instead make use of `Array.find` to select the node from day5 Array with the condition
    // var day5Items = day5[idx];
    var day5Items = day5.find((node) => node.type === day1Items.type)
    var outputElements = {};
    if(day1Items && day5Items){            
      if(day1Items.type == day5Items.type){ //Here, I am not getting how to get the matched value between two array and proceed.
        outputElements.id = day1Items.id;
        outputElements.type = day1Items.type;
        outputElements.caseCount = day1Items.cases;
        outputElements.failCount = day1Items.fail;
        outputElements.difference = day1Items.cases - day5Items.cases;//Here, I need to get the cases value respective type matched
        // Calculation was wrong here
        outputElements.diffPercentage = ((day1Items.cases - day5Items.cases)/(day5Items.cases)*100).toFixed(2);
        result.push(outputElements);
      }
    }
});

console.log(result);

简化方法

使用Array.reduce

var day1 = [
  { id: 1, type: "20H", cases: 30, fail: 5 }, 
  { id: 1, type: "12C", cases: 10, fail: 3 }, 
  { id: 1, type: "4B", cases: 20, fail: 8 }, 
  { id: 1, type: "49B", cases: 20, fail: 8 } 
];;

var day5 = [
  { id: 5, type: "12C", cases: 5, fail: 2 },
  { id: 5, type: "4B", cases: 12, fail: 3 },
  { id: 5, type: "20H", cases: 20, fail: 6 },
];

const result = day1.reduce((acc, curr) => {
  const insertNode = { id: curr.id, type: curr.type, caseCount: curr.cases, failCount: curr.fail };
  const d5Node = day5.find((node) => node.type === curr.type);
  if (d5Node) {
    insertNode.difference = curr.cases - d5Node.cases;
    insertNode.diffPercentage = (insertNode.difference / d5Node.cases * 100).toFixed(2);
  } else {
    // Handle the calculation logic here
    insertNode.difference = curr.cases;
    insertNode.diffPercentage = insertNode.difference * 100;
  }
  acc.push(insertNode);
  return acc;
}, []);
console.log(result);