遍歷一個對象數組並根據條件添加到其他數組

Question

我有一個包含以下對象的數組。

var notTotal = [{"Year":2012,"Value":800579}, 
       {"Year":2012,"Value":654090}, 
       {"Year":2012,"Value":758092}, 
       {"Year":2013,"Value":343928},...More objects.. ] 

我想要做的是遍歷這個對象數組，其中只有一年存在而不是多個，並且將當年的值加起來。用上面的例子..

var total = [{"Year":2012,"Value":2556689}, 
//Total of first three 2012 assuming there isnt anymore 2012 in the array 
      {"Year":2013,"Value":343928},...] 

我已經試過類似如下：

for(var i = 0; i < notTotal.length; i++) { 
    if (total.includes(notTotal[i].Year || notTotal[i])) { 
     //Add the value of the year in notTotal array to the same year in total array 
    } else { 
    total.push(notTotal[i]); //add year and value if it does not exist to the total array 
} 
} 

道歉，如果這是一個重複。這似乎是一個非常具體的問題。

謝謝！

Answer 1

一個簡單的解決方案是創建一個對象，持有總量按年份。

var totalByYear = {}; 

然後，您可以使用循環的notTotal.forEach陣列或for循環，你已經證明，增加了有關今年totalByYear物體內部的價值在。

notTotal.forEach(function(ele) { totalByYear[ele.Year] += ele.Value }); 

這產生具有年份鍵和總值的對象，例如，使用例如：

{'2012': 2556689, '2013': 343928 /* other years */} 

所述期望的格式（對於D3）然後可以從totalByYear對象（以及由年總計印刷）內置：

var totals = []; 
for (year in totalByYear) { 
    console.log('Total for year ' + year + ' is ' + totalByYear[year]); 
    //Build the correctly formatted array 
    totals.push({ Year: year, Value: totalByYear[year]}); 
} 

//Prints: 
//Total for year 2012 is 2556689 
//etc.etc. 

的totals陣列然後將具有所需格式。

Answer 2

，你可以建立一個哈希表：

var hash = {},total=[]; 
for(const {Year,Value} of notTotal){ 
    if(hash[Year]){ 
    hash[Year].Value+=Value; 
    }else{ 
    total.push(hash[Year]={Year,Value}); 
    } 
} 

In action

注：對象屬性通常不大寫...

Answer 3

偉大的問題！要解釋您的if (total.includes(notTotal[i].Year || notTotal[i]))中發生的情況是，您正在通過total陣列查看一年中的數據，或者僅僅是現有的notTotal[i]。所以你的循環試圖找到一個值正好是2012或正好"Year":2012,"Value":2556689。 ERGO，如果你的total數組是這樣的：

[{"Year":2012, "Value": 12345}] 

你的循環將找不到它，即使沒有與2012爲一年的對象。至於如何解決這個問題，請看看前面的問題！

How to determine if Javascript array contains an object with an attribute that equals a given value?

希望幫助:)

Answer 4

你可以使用一個哈希表，並檢查今年不存在，然後生成一個新的結果集。然後更新總數。

var values = [{ Year: 2012, Value: 800579 }, { Year: 2012, Value: 654090 }, { Year: 2012, Value: 758092 }, { Year: 2013, Value: 343928 }], 
 
    hash = Object.create(null), 
 
    totals = []; 
 
    
 
values.forEach(function (o) { 
 
    hash[o.Year] || totals.push(hash[o.Year] = { Year: o.Year, Value: 0 }); 
 
    hash[o.Year].Value += o.Value; 
 
}); 
 

 
console.log(totals);

Answer 5

var notTotal = [{"Year":2012,"Value":800579}, 
 
       {"Year":2012,"Value":654090}, 
 
       {"Year":2012,"Value":758092}, 
 
       {"Year":2013,"Value":343928}] 
 
       
 
var totalObj = notTotal.reduce((sum, obj) => { 
 
    sum[obj.Year] = sum[obj.Year] + obj.Value || obj.Value; 
 
    return sum; 
 
}, {}); 
 

 
// convert total to the format you need; 
 
var total = Object.entries(totalObj).map(([Year, Value]) => ({Year, Value})) 
 

 
console.log(total);

Answer 6

多了一個解決方案：

function yearlyValueFilter(array){ 
    var yearlyValue = {} 
    array.forEach((obj) => { //litterate on the input 
    var year = obj.Year 
    var value = obj.Value 
    if((year in yearlyValue)){ //if the array with not duplicated years conatins the litteration year just plus that value 
     yearlyValue[year] += value 
    }else{  //if not conatins, it gets as a basic value 
     yearlyValue[year] = value 
    } 
    }) 
    return yearlyValue 
}