我有一个对象数组：
var array = [{
id: "cards",
amount: 5
}, {
id: "shirts",
amount: 3
}, {
id: "cards",
amount: 2
}, {
id: "shirts",
amount: 3
}]
我需要做的是遍历这个数组并找到所有id类型的总和。 所以在这个例子中，我会找到卡片和衬衫的总数。
我不确定如何使用对象执行此操作。我尝试用Object.values(array)剥离对象，但有没有办法用对象做到这一点？
感谢您的帮助。
答案 0 :(得分：1)
您将遍历数组，检查目标对象的id属性，然后使用amount属性中存储的值枚举和外部范围变量。
var totalShirts = 0;
var totalCards = 0;
for(var i = 0, len = array.length; i < len; i++){
var entry = array[i];
if(entry.id === "cards"){
totalCards += entry.amount;
}
else if(entry.id === "shirts"){
totalShirts += entry.amount;
}
}
console.log("Total Cards: " + totalCards);
console.log("Total Shirts: " + totalShirts);
答案 1 :(得分：1)
以下是获取每个项目总数的示例
var array = [{id:"cards", amount: 5}, {id:"shirts", amount: 3}, {id:"cards", amount: 2}, {id:"shirts", amount: 3}];
var result = array.reduce(function(accumulator, current) {
if (!(current.id in accumulator)) {
accumulator[current.id] = current.amount;
} else {
accumulator[current.id] += current.amount;
}
return accumulator;
}, {});
console.log(result);
答案 2 :(得分：1)
这应该做你想要的：
.bold {
font-weight: bold;
}
答案 3 :(得分：1)
一个简单的 ...
<ItemsControl Grid.Row="1" ItemsSource="{Binding SelectedUnit.LocalControllerInfo.Inputs}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Margin="10" FontSize="15" Style="{StaticResource TextBlockNormalBase}" Text="{Binding InputName}"/>
<StackPanel Orientation="Horizontal">
<RadioButton Margin="10" Foreground="White" Content="Normal"
IsChecked="{Binding Path=?,
Converter={StaticResource inputToBoolConverter},
ConverterParameter=?}"/>
<RadioButton Margin="10" Foreground="White" Content="Active"
IsChecked="{Binding Path=?,
Converter={StaticResource inputToBoolConverter},
ConverterParameter=?}"/>
</StackPanel>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
...
可以解决问题：
public class Unit : BindableObject
{
public enum InputState
{
Normal,
Active
}
private LocalControllerTypes.LocalController _localControllerInfo;
private LocalControllerTypes.ArduinoInjector[] _arduinoInjector;
private WebWriter.WebWriter[] _inputWriters;
private SNMPNetworkSwitchConnection.SNMPNetworkSwitchConnection _networkSwitchConnection;
private InputState[] _inputStates;
private bool _isUnitConnected;
public Unit(LocalControllerTypes.LocalController localControllerInfo,
LocalControllerTypes.ArduinoInjector[] arduinoInjector,
WebWriter.WebWriter[] inputWriters,
SNMPNetworkSwitchConnection.SNMPNetworkSwitchConnection networkSwitchConnection)
{
_localControllerInfo = localControllerInfo;
_arduinoInjector = arduinoInjector;
_inputWriters = inputWriters;
_networkSwitchConnection = networkSwitchConnection;
// This assumption might not always be true, but there is no way for now to get the input state
_inputStates = Enumerable.Repeat(InputState.Normal, _inputWriters.Length).ToArray();
// This assumption might not always be true, but there is no way for now to get the connection state
_isUnitConnected = true;
}
public LocalControllerTypes.LocalController LocalControllerInfo
{
get
{
return _localControllerInfo;
}
set
{
if (_localControllerInfo != value)
{
_localControllerInfo = value;
RaisePropertyChanged();
}
}
}
public LocalControllerTypes.ArduinoInjector[] ArduinoInjectors
{
get
{
return _arduinoInjector;
}
set
{
if (_arduinoInjector != value)
{
_arduinoInjector = value;
RaisePropertyChanged();
}
}
}
public WebWriter.WebWriter[] InputWriters
{
get
{
return _inputWriters;
}
set
{
if (_inputWriters != value)
{
_inputWriters = value;
RaisePropertyChanged();
}
}
}
public SNMPNetworkSwitchConnection.SNMPNetworkSwitchConnection NetworkSwitchConnection
{
get
{
return _networkSwitchConnection;
}
set
{
if (_networkSwitchConnection != value)
{
_networkSwitchConnection = value;
RaisePropertyChanged();
}
}
}
public InputState[] InputStates
{
get
{
return _inputStates;
}
set
{
if (_inputStates != value)
{
_inputStates = value;
RaisePropertyChanged();
}
}
}
public bool IsUnitConnected
{
get
{
return _isUnitConnected;
}
set
{
if (_isUnitConnected != value)
{
_isUnitConnected = value;
RaisePropertyChanged();
}
}
}
}
将打印：
public class MainViewModel : INotifyPropertyChanged
{
private Unit _selectedUnit;
private ObservableCollection<Unit> _units;
private string _reader1RawCardData;
private string _reader2RawCardData;
private int _reader1BitsCount;
private int _reader2BitsCount;
public event PropertyChangedEventHandler PropertyChanged;
public MainViewModel(IUnitStore unitStore)
{
UnitStore = unitStore;
// We could use directly the unitstore instead of creating another container and binding on that, but
// not doing so will allow us to add unit filtering further down the road
_units = new ObservableCollection<Unit>(unitStore.Units);
_selectedUnit = _units.First();
_reader1RawCardData = "";
_reader2RawCardData = "";
_reader1BitsCount = 0;
_reader2BitsCount = 0;
}
protected void RaisePropertyChanged([CallerMemberName]string propertName = "")
{
var temp = PropertyChanged;
if (temp != null)
{
temp(this, new PropertyChangedEventArgs(propertName));
}
}
protected void RefreshUnitStore(object obj)
{
UnitStore.UpdateStore();
Units = new ObservableCollection<Unit>(UnitStore.Units);
SelectedUnit = Units.First();
}
protected void SendReaderCardSwipe(object obj)
{
int unitReaderNumber = (int)obj;
IPAddress arduinoIp = SelectedUnit.LocalControllerInfo.Readers[unitReaderNumber - 1].InjectorIp;
int injectorNumber = SelectedUnit.LocalControllerInfo.Readers[unitReaderNumber - 1].InjectorNumber;
string serviceUrl = SelectedUnit.ArduinoInjectors.Where(injector => injector.Ip.Equals(arduinoIp)).First().Url;
InjectorInterface.CardSwipe<IPAddress>(serviceUrl, arduinoIp, injectorNumber, Reader1BitsCount, Reader1RawCardData);
}
protected void UpdateSelectedUnitConnectionState(object obj)
{
((INetworkConnection.INetworkConnection)SelectedUnit.NetworkSwitchConnection).SetConnection(SelectedUnit.IsUnitConnected);
}
public IUnitStore UnitStore
{
get;
private set;
}
public Unit SelectedUnit
{
get
{
return _selectedUnit;
}
set
{
if (_selectedUnit != value)
{
_selectedUnit = value;
RaisePropertyChanged();
}
}
}
public ObservableCollection<Unit> Units
{
get
{
return _units;
}
set
{
if (_units != value)
{
_units = value;
RaisePropertyChanged();
}
}
}
public string Reader1RawCardData
{
get
{
return _reader1RawCardData;
}
set
{
if (_reader1RawCardData != value)
{
_reader1RawCardData = value;
RaisePropertyChanged();
}
}
}
public string Reader2RawCardData
{
get
{
return _reader2RawCardData;
}
set
{
if (_reader2RawCardData != value)
{
_reader2RawCardData = value;
RaisePropertyChanged();
}
}
}
public int Reader1BitsCount
{
get
{
return _reader1BitsCount;
}
set
{
if (_reader1BitsCount != value)
{
_reader1BitsCount = value;
RaisePropertyChanged();
}
}
}
public int Reader2BitsCount
{
get
{
return _reader2BitsCount;
}
set
{
if (_reader2BitsCount != value)
{
_reader2BitsCount = value;
RaisePropertyChanged();
}
}
}
public ICommand RefreshSourceCommand
{
get
{
return new RelayCommand(RefreshUnitStore);
}
}
public ICommand SendReaderCardSwipeCommand
{
get
{
return new RelayCommand(SendReaderCardSwipe);
}
}
public ICommand UpdateSelectedUnitConnectionStateCommand
{
get
{
return new RelayCommand(UpdateSelectedUnitConnectionState);
}
}
}
答案 4 :(得分：0)
您可以使用Array#reduce并将金额相加。
var array = [{ id: "cards", amount: 5 }, { id: "shirts", amount: 3 }, { id: "cards", amount: 2 }, { id: "shirts", amount: 3 }],
result = array.reduce(function (r, a) {
r[a.id] = (r[a.id] || 0) + a.amount;
return r;
}, {});
console.log(result);
答案 5 :(得分：0)
这是一个O（n）时间解决方案。
var totals = new Object();
for(var i = 0;i < array.length;i ++) {
var id = array[i].id;
var amount = array[i].amount;
if(totals[id] == undefined) {
totals[id] = amount;
} else {
totals[id] += amount;
}
}
console.log(totals);
答案 6 :(得分：0)
您可以使用for..of循环
var array = [{
id: "cards",
amount: 5
}, {
id: "shirts",
amount: 3
}, {
id: "cards",
amount: 2
}, {
id: "shirts",
amount: 3
}]
let res = {};
for (let {id,amount} of array) {
if (!res.hasOwnProperty(id)) res[id] = 0;
res[id] += amount;
}
console.log(res);
答案 7 :(得分：0)
使用for循环执行此操作：
var totalCards = 0;
var totalShirt = 0;
for (var i = 0; i < arr.length; i++) {
if (arr[i].id === "cards") {
totalCards += arr[i].amount;
} else {
totalShirt += arr[i].amount;
}
}
答案 8 :(得分：0)
for for循环中的魔力。这个例子应该足够通用：
var array = [ {id:"cards", amount: 5}, {id:"shirts", amount: 3}, {id:"cards", amount: 2}, {id:"shirts", amount: 3} ];
var output = [];
for(var i of array) {
if(!output[i.id]) {
output[i.id] = 0;
}
output[i.id] += i.amount;
}
console.log(output);
答案 9 :(得分：0)
var array = [{id:"cards", amount: 5}, {id:"shirts", amount: 3}, {id:"cards", amount: 2}, {id:"shirts", amount: 3}];
var arr = [];
array.forEach(v => arr.push(v.id));
var newArr = [...new Set(arr)];
var arr2 = [];
newArr.forEach(function(v) {
var obj = {};
obj.id = v;
obj.counter = 0;
arr2.push(obj);
});
arr2.forEach(v => array.forEach(c => c.id == v.id ? v.counter += c.amount : v));
console.log(arr2);
答案 10 :(得分：0)
您可以使用Array.forEach()迭代数组的每个元素。总对象是一个关联数组，其中索引是数组元素对象的id字段。
var array = [{ id: "cards", amount: 5 },
{ id: "shirts", amount: 3 },
{ id: "cards", amount: 2},
{ id: "shirts", amount: 3 }];
var total = {};
array.forEach(function (el) {
if (total[el.id]) {
total[el.id] += el.amount
} else {
total[el.id] = el.amount
}
});
console.log(JSON.stringify(total));
答案 11 :(得分：-1)
您可以使用此代码
if (!Object.keys) {
Object.keys = function (obj) {
var keys = [],
k;
for (k in obj) {
if (Object.prototype.hasOwnProperty.call(obj, k)) {
keys.push(k);
}
}
return keys;
};
}
然后您也可以在旧浏览器中执行此操作：
var len = Object.keys(obj).length;