面试题中往往会遇到这样的笔试题，将以下数组对象合并相同值
var arr = [{"name": "语文","fraction": 80}, {"name": "数学","fraction": 70}, {"name": "语文","fraction": 50}, {"name": "语文","fraction": 90}, {"name": "数学","fraction": 100}, {"name": "数学","fraction": 55}, {"name": "语文","fraction": 99}]
在实际项目中，我们经常会遇到这种格式的数据，这种格式让人阅读起来很不直观，而且不利于代码的维护。废话不多说了直接上代码
第一种方式：
arr = arr.map(function(item, index, arr) {const i = arr.find(_item => item.name === _item.name);if(i !== item) {i.fraction.push(item.fraction);return undefined;} else {i.fraction = [i.fraction];return i;}}).filter(item => item !== undefined);
输出结果：[{"name": "语文","fraction": [80, 50, 90, 99]}, {"name": "数学","fraction": [70, 100, 55]}, {"name": "英语","fraction": [55, 89]}]
第二种方式：推荐
var res =[];var narr=[];for(var i =0;i<arr.length;i++){var n = res.indexOf(arr[i].name);if(n == -1){res.push(arr[i].name);narr.push({"name":arr[i].name,fraction:[arr[i].fraction]})}else{narr[n].fraction.push(arr[i].fraction)}}console.log(narr)
输出结果：[{"name": "语文","fraction": [80, 50, 90, 99]}, {"name": "数学","fraction": [70, 100, 55]}, {"name": "英语","fraction": [55, 89]}]
