for和findIndex循环的替代选项？
for和findIndex循环的替代选项？
提问于 2019-11-25 01:15:26
我目前正在使用for和findIndex来更新主result变量中的总数。有没有其他方法可以重写这段代码，使其更短或更具可读性？
const payload = [
{ Id: 1, Total: 5 },
{ Id: 3, Total: 2 },
]
const result = {
Items: [
{ Id: 1, Name: 'Item 1 A', Total: 1, Type: "Main"},
{ Id: 1, Name: 'Item 1 B', Total: 0},
{ Id: 2, Name: 'Item 2 C', Total: 1, Type: "Main"},
{ Id: 2, Name: 'Item 2 D', Total: 0},
{ Id: 3, Name: 'Item 3 E', Type: "Main"},
{ Id: 3, Name: 'Item 3 F', Total: 0},
]
}
for(const itemPayload of payload) {
const itemIndex = result.Items.findIndex(item => item.Id === itemPayload.Id && item.Type === "Main");
if (itemIndex !== -1) {
result.Items[itemIndex].Total = itemPayload.Total;
}
}
console.log(result);
回答 4
Stack Overflow用户
发布于 2019-11-25 01:50:43
在这里，我们创建了一个Map，然后在循环中访问它。它更整洁，可读性更好。
const payload = [
{ Id: 1, Total: 5 },
{ Id: 3, Total: 2 },
]
const result = {
Items: [
{ Id: 1, Name: 'Item 1 A', Total: 1, Type: "Main" },
{ Id: 1, Name: 'Item 1 B', Total: 0 },
{ Id: 2, Name: 'Item 2 C', Total: 1, Type: "Main" },
{ Id: 2, Name: 'Item 2 D', Total: 0 },
{ Id: 3, Name: 'Item 3 E', Type: "Main" },
{ Id: 3, Name: 'Item 3 F', Total: 0 },
]
};
const payloadMap = payload.reduce((map, obj) => {
map[obj.Id] = obj.Total;
return map;
}, {});
result.Items = result.Items.map(item => {
if (item.Type === 'Main' && payloadMap[item.Id]) {
item.Total = payloadMap[item.Id];
}
return item;
});
console.log(result);
Stack Overflow用户
发布于 2019-11-25 01:20:50
您可以将有效负载转换为映射，然后仅循环result.Items一次(而不是通过findIndex重复执行)：
const payloadMap = new Map(payload.map(({Id, Total}) => [Id, Total]));
for (const item of result.Items) {
if (item.Type === "Main") {
const total = payloadMap.get(item.Id);
if (total !== undefined) {
item.Total = total;
}
}
}现场示例：
const payload = [
{ Id: 1, Total: 5 },
{ Id: 3, Total: 2 },
]
const result = {
Items: [
{ Id: 1, Name: 'Item 1 A', Total: 1, Type: "Main"},
{ Id: 1, Name: 'Item 1 B', Total: 0},
{ Id: 2, Name: 'Item 2 C', Total: 1, Type: "Main"},
{ Id: 2, Name: 'Item 2 D', Total: 0},
{ Id: 3, Name: 'Item 3 E', Type: "Main"},
{ Id: 3, Name: 'Item 3 F', Total: 0},
]
}
// Convert the payload to a Map:
const payloadMap = new Map(payload.map(({Id, Total}) => [Id, Total]));
// Loop through `result.Items` just once:
for (const item of result.Items) {
if (item.Type === "Main") {
const total = payloadMap.get(item.Id);
if (total !== undefined) {
item.Total = total;
}
}
}
console.log(result);
映射针对随机访问检索进行了优化。
另一种选择是除了result中的type = "Main"项的数组之外，还可以有一个Map of add项，两者都引用相同的对象，但这意味着当您向数组添加/从数组中删除时，您还必须在Map中添加/删除。
Stack Overflow用户
发布于 2019-11-25 01:21:03
如果这就是你要找的，你可以试试这样的东西。
const payload = [{
Id: 1,
Total: 5
},
{
Id: 3,
Total: 2
},
]
const result = {
Items: [{
Id: 1,
Name: 'Item 1 A',
Total: 1,
Type: "Main"
},
{
Id: 1,
Name: 'Item 1 B',
Total: 0
},
{
Id: 2,
Name: 'Item 2 C',
Total: 1,
Type: "Main"
},
{
Id: 2,
Name: 'Item 2 D',
Total: 0
},
{
Id: 3,
Name: 'Item 3 E',
Type: "Main"
},
{
Id: 3,
Name: 'Item 3 F',
Total: 0
},
]
}
let newdata = result.Items.map(ele => {
if (ele.Type == "Main") {
let payload_ = payload.find(e => e.Id == ele.Id);
if (payload_) {
ele.Total = payload_.Total;
}
}
return ele;
})
console.log(newdata);
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/59020315
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