分組概括

Question

我有一個JSON對象數組這樣

var scores= [{sectionid:1,sectiontitle:'Section1',score:5}, 
{sectionid:1,sectiontitle:'Section1',score:15}, 
{sectionid:1,sectiontitle:'Section1',score:7}, 
{sectionid:1,sectiontitle:'Section1',score:4}, 
{sectionid:2,sectiontitle:'Section2',score:5}, 
{sectionid:2,sectiontitle:'Section2',score:45}, 
{sectionid:2,sectiontitle:'Section2',score:13}, 
{sectionid:3,sectiontitle:'Section3',score:6}, 
{sectionid:3,sectiontitle:'Section3',score:23}, 
{sectionid:3,sectiontitle:'Section3',score:9}, 
{sectionid:3,sectiontitle:'Section3',score:12}, 
{sectionid:3,sectiontitle:'Section3',score:55}, 
{sectionid:4,sectiontitle:'Section4',score:4}, 
{sectionid:4,sectiontitle:'Section4',score:35}]; 

但我需要得到這些組JSON對象數組與另一個變量分組總分就在裏面。

因此所產生的變量應該是這樣的

var result=[{sectionid:1,sectiontitle:'Section1',score:26}, 
{sectionid:2,sectiontitle:'Section2',score:63}, 
{sectionid:3,sectiontitle:'Section3',score:105}, 
{sectionid:4,sectiontitle:'Section4',score:39}]; 

我嘗試使用各種功能的穿越得分變量。但發現很複雜。我們如何才能以最好，最快捷的方式使其成爲可能

Answer 1

使用.forEach和sectionId作爲構建新陣列的唯一鍵。我也用indexMap快速索引查找：

var indexMap = {}; 
var result = []; 
scores.forEach(function (item) { 
    var index = indexMap[item.sectionid]; 
    if (typeof index !== 'undefined') { 
     result[index].score += item.score; 
    } else { 
     indexMap[item.sectionid] = result.push(item) - 1; 
    } 
}); 
console.log(result); 

小提琴例如：http://jsfiddle.net/7a6u38hd/

Answer 2

試試這個

var ct = {}; 
for(var i=0;i<scores.length;i++) { 
    var tp= scores[i]; 
    var x = ct[tp.sectionid]; 
    if(x) { 
     x = tp; 
     x.score = x.score + tp.score; 
    } else { 
     x = tp; 
    } 
}