如何循环遍历 JavaScript 对象并对新对象中的金额求和

Question

我有一个 javascript 对象，

const data = {
  type: "FeatureCollection",
  features: [{
    type: "Feature",
    geometry: {
      type: "Point",
      coordinates: [-118.4158548, 33.9811315]
    },
    properties: {
      name: "John Smith",
      total_due: 1
    }
  }, {
    type: "Feature",
    geometry: {
      type: "Point",
      coordinates: [-122.4605458, 37.7286008]
    },
    properties: {
      name: "June Waters",
      total_due: 50
    }
  }, {
    type: "Feature",
    geometry: {
      type: "Point",
      coordinates: [-122.4120835, 37.7778926]
    },
    properties: {
      name: "John Smith",
      total_due: 2
    }
  }, {
    type: "Feature",
    geometry: {
      type: "Point",
      coordinates: [-118.3508279, 34.0701918]
    },
    properties: {
      name: "June Waters",
      total_due: 60
    }
  }, {
    type: "Feature",
    geometry: {
      type: "Point",
      coordinates: [-82.4000143, 34.8518747]
    },
    properties: {
      name: "Mike Jones",
      total_due: 30
    }
  }]
};

我想做的是循环访问该对象，将唯一名称添加到新对象中并对总数进行求和。新对象看起来像这样：

newObject = {'June Waters':110, 'Mike Jones':30, 'John Smith': 3}

我尝试执行以下操作，但我对 JS 很陌生，所以我不知道我在做什么。

var newObject = {}
  
data.features.forEach(function (item) {
  newObject.item.properties.name = newObject.item.properties.name + item.properties.total_due
});

以下是生成的错误的一部分。

TypeError: Cannot read properties of undefined (reading 'properties')
    at c:\Users\ryanj\z\const data =.js:10:18
    at Array.forEach (<anonymous>)....

任何帮助或提示将不胜感激。

Answer 1

您遇到了错误，因为 newObject.item 是 未定义，因为空对象因此您尝试访问的任何属性（例如 properties）都不是 来发现

通过对您的实现进行一些调整 。我将名称添加到 newObject 中（如果它不存在），然后我继续添加总计

const data = {"type": "FeatureCollection","features": [{"type": "Feature","geometry": {"type": "Point","coordinates": [-118.4158548, 33.9811315]},"properties": {"name": "John Smith","total_due": 1}},{"type": "Feature","geometry": {"type": "Point","coordinates": [-122.4605458, 37.7286008]},"properties": {"name": "June Waters","total_due": 50}},{"type":"Feature","geometry": {"type": "Point","coordinates": [-122.4120835, 37.7778926]},"properties": {"name": "John Smith","total_due": 2}},{"type": "Feature","geometry": {"type": "Point","coordinates": [-118.3508279, 34.0701918]},"properties": {"name": "June Waters","total_due": 60}},{"type": "Feature","geometry": {"type": "Point","coordinates": [-82.4000143, 34.8518747]},"properties": {"name": "Mike Jones","total_due": 30}}]};

var newObject = {}
  
data.features.forEach(function (item) {
    if(!newObject[item.properties.name])newObject[item.properties.name] = 0;
  newObject[item.properties.name] = newObject[item.properties.name] + item.properties.total_due
});

console.log(newObject)

同样，您可以使用reduce来解决这些类型的问题

const data = {"type": "FeatureCollection","features": [{"type": "Feature","geometry": {"type": "Point","coordinates": [-118.4158548, 33.9811315]},"properties": {"name": "John Smith","total_due": 1}},{"type": "Feature","geometry": {"type": "Point","coordinates": [-122.4605458, 37.7286008]},"properties": {"name": "June Waters","total_due": 50}},{"type":"Feature","geometry": {"type": "Point","coordinates": [-122.4120835, 37.7778926]},"properties": {"name": "John Smith","total_due": 2}},{"type": "Feature","geometry": {"type": "Point","coordinates": [-118.3508279, 34.0701918]},"properties": {"name": "June Waters","total_due": 60}},{"type": "Feature","geometry": {"type": "Point","coordinates": [-82.4000143, 34.8518747]},"properties": {"name": "Mike Jones","total_due": 30}}]};

let total = data.features.reduce((acc,curr) =>{
    if(!acc[curr.properties.name])acc[curr.properties.name]=0;
  acc[curr.properties.name]+=curr.properties.total_due;
  return acc;
},{})

console.log(total)

Answer 2

在 Javascript 中，您可以使用方括号 [] 引用对象属性，就像我们在数组中所做的那样。

在这段代码中，我们首先检查对象中是否已经定义了键。如果未定义，我们将简单地将total_due 的值分配给键（在本例中是人名）。在下一次迭代中，如果 Javascript 识别出该键并且该键的值不是未定义的，我们只需将 total_due 值添加到当前键值即可。

let finalData = {}
data.features.forEach((item) => {
    if (finalData[item.properties.name] === undefined) {
        finalData[item.properties.name] = item.properties.total_due;
    }
    else {
        finalData[item.properties.name] += item.properties.total_due;
    }
})