JavaScript数组中的循环增加办法
一、JS对象数组各个值相加
var dataList = [
{ id: 1, price: 5.5, amount: 3 },
{ id: 2, price: 1.5, amount: 5 },
{ id: 3, price: 3.5, amount: 8 },
{ id: 4, price: 5.5, amount: 2 },
{ id: 5, price: 0.5, amount: 7 },
{ id: 6, price: 1.5, amount: 4 },
{ id: 7, price: 6.5, amount: 9 }
];
function arrOperate (allData) {
let newArr = [], obj = {};
allData.forEach(item => {
for (let key in item) {
let value = item[key];
key in obj ? (obj[key] += value) : (obj[key] = value);
}
});
for (let i in obj) {
let o = {};
o[i] = obj[i];
newArr.push(o);
};
console.log(newArr); // [ { id: 28 }, { price: 24.5 }, { amount: 38 } ]
}
arrOperate(dataList);二、JS对象数组key值相等value相加
let arr = [{ "语文": 100, "数学": 100 },
{ "语文": 100, "数学": 100 },
{ "语文": 100, "数学": 100, "英语": 100 },
{ "语文": 100, "数学": 100, "物理": 100 },
{ "英语": 100, "化学": 100 }, ];
let newArr = [], obj = {};
arr.forEach(item => {
for(let key in item) {
let value = item[key];
key in obj ? (obj[key] += value) : (obj[key] = value)
}
});
//遍历对象转为数组
for(let i in obj) {
let o = {};
o[i] = obj[i];
newArr.push(o)
}
console.log(newArr); // [{语文：400},{数学：400},{英语：200},{物理：100},{化学：100}]三、JS数组对象的去重和排序操作
// 合并相同价格(price)的数量(amount)并以价格从小到大排序
var dataList = [
{ id: 1, price: 5.5, amount: 3 },
{ id: 2, price: 1.5, amount: 5 },
{ id: 3, price: 3.5, amount: 8 },
{ id: 4, price: 5.5, amount: 2 },
{ id: 5, price: 0.5, amount: 7 },
{ id: 6, price: 1.5, amount: 4 },
{ id: 7, price: 6.5, amount: 9 }
]；
// 排序方法
function compare(prop) {
return function(a, b) {
return a[prop] - b[prop]
}
}
dataList.sort(compare('price'))
// 最终的数据
var newArray = []
// 空对象
var newObject = {}
// 重复的数据
var otherArray = []
// 利用对象访问属性的方法，判断对象中是否存在price
dataList.forEach(v => {
if (!newObject[v.price]) {
newObject[v.price] = true
newArray.push(v)
} else {
otherArray.push(v)
}
});
// 合并数量的操作
otherArray.forEach(v => {
newArray.forEach(k => {
if (v.price === k.price) {
k.amount += v.amount
}
});
});
// [{"id":5,"price":0.5,"amount":7},{"id":2,"price":1.5,"amount":9}, {"id":3,"price":3.5,"amount":8}，{"id":1,"price":5.5,"amount":5},{"id":7,"price":6.5,"amount":9}]
console.log(newArray)；四、js计算数组里的对象的某个值相同，其余值相加
let arry=[ {Code:'x',Quantity:1,ItemType:'normal'},
{Code:'x',Quantity:2,ItemType:'normal'},
{Code:'x',Quantity:5,ItemType:'normal'},
{Code:'y',Quantity:1,ItemType:'spec'},
{Code:'y',Quantity:2,ItemType:'spec'},
{Code:'z',Quantity:1,ItemType:'normal'} ];
let newfood=[];
var temp = {};
for(var i in arry) {
var key= arry[i].Code;
if(temp[key]) {
temp[key].Code = temp[key].Code ;
temp[key].Quantity = temp[key].Quantity+ arry[i].Quantity;
} else {
temp[key] = {};
temp[key].Code = arry[i].Code;
temp[key].Quantity = arry[i].Quantity;
}
temp[key].ItemType= arry[i].ItemType;
}
for(var k in temp){
newfood.push(temp[k])
}
alert(JSON.stringify(newfood));
//[{"Code":"x","Quantity":8,"ItemType":"normal"},{"Code":"y","Quantity":3,"ItemType":"spec"},{"Code":"z","Quantity":1,"ItemType":"normal"}] 五、js根据对象数组中某一属性值，合并相同项，并对某一属性累加处理
let data = [
{ code: 1001, name: '苹果', sl: 11 },
{ code: 1001, name: '苹果', sl: 11 },
{ code: 1001, name: '苹果', sl: 11 },
{ code: 1001, name: '苹果', sl: 11 },
{ code: 1002, name: '西瓜', sl: 11 },
{ code: 1002, name: '西瓜', sl: 15 },
{ code: 1003, name: '梨', sl: 15 },
{ code: 1003, name: '梨', sl: 15 },
];
// 第一种：根据对象key的唯一性，累加sl值
let item = {};
for (let i = 0; i < data.length; i++) {
item[data[i].code] = ~~item[data[i].code] + data[i].sl
}
console.log(item); // 结果： {1001: 44, 1002: 26, 1003: 30}
//第二种：根据reduce遍历累加，得到数组
let newArray = data.reduce((total, cur, index) => {
let hasValue = total.findIndex(current => { return current.code === cur.code});
hasValue === -1 && total.push(cur);
hasValue !== -1 && (total[hasValue].sl = total[hasValue].sl + cur.sl);
return total;
}, []);
console.log(newArray); // 结果： [{code: 1001, name: "苹果", sl: 44}, {code: 1002, name: "西瓜", sl: 26}, {code: 1003, name: "梨", sl: 30}]六、又一个循环添加
var arry= [
{key:'a',value:2},
{key:'a',value:2},
{key:'a',value:2},
{key:'b',value:8}
]
// 第一种
let target = [];
let keysArr =[...new Set( arry.map(item=>item.key))] ;
keysArr.forEach(item=>{
const arr = arry.filter(keys=>keys.key == item);
const sum = arr.reduce((a,b)=>a+b.value,0)
target.push({
key:item,
value:sum
})
})
console.log(target)
// 第二种方式
var newArr = [...arry.reduce((m, x) => m.set(x.key, (m.get(x.key) || 0) + x.value), new Map())].map(([key, value]) => ({ key, value }))
console.log(newArr)
// 第三种方式
function keyPlusValue(arr) {
const result = arr.reduce((obj, item) => {
if (!obj[item.key]) {
obj[item.key] = 0
}
obj[item.key] += item.value
return obj
}, {})
return Object.keys(result).map(key => ({key: key, value: result[key]}))
}
console.log(keyPlusValue(arry))
// 第四种方式
let newArr = arry.reduce((resp, obj)=> {
var originObj = resp.find(item => item.key === obj.key);
if (originObj) {
originObj.value+= obj.value;
} else {
resp.push(obj)
}
return resp;
}, [])
console.log(newArr)结果：
七、
//问题一：js中根据数组对象中的相同id值进行合并，并将name值合并，并且用逗号隔开返回新的数组对象
let dataArr = [
{ id:1, name:"A", score:10 },
{ id:2, name:"B", score:20 },
{ id:1, name:"C", score:30 },
{ id:2, name:"D", score:40 }
];
//将dataArr赋值给beforeData 也可直接操作dataArr
var beforeData = dataArr;
let tempArr = [];
let afterData = [];//新数组
for (let i = 0; i < beforeData.length; i++) {
if (tempArr.indexOf(beforeData[i].id) === -1) {
afterData.push({
id: beforeData[i].id,
score: beforeData[i].score,
name: [beforeData[i].name],
});
tempArr.push(beforeData[i].id);
} else {
for (let j = 0; j < afterData.length; j++) {
if (afterData[j].id == beforeData[i].id) {
afterData[j].name.push(beforeData[i].name);
break;
}
}
}
}
//循环afterData并且合并name值用逗号隔开
afterData.map((item) => {
item.name= item.name.join(",");
});
console.log(afterData);