如何遍历 javascript 对象并在新对象中求和

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
    }
  }]
};

我想做的是遍历对象，将唯一名称添加到新对象并求和。新对象将如下所示：

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，所以我不知道自己在做什么。

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>)....

如有任何帮助或提示，我们将不胜感激。

Answer 1

你运行出错了，因为 newObject.item 是 undefined 因为空对象因此你试图访问的任何属性都超出了 properties未找到

通过对您的实施进行一些调整。我将名称添加到 newObject 如果它已经不存在然后我继续添加总数

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)

类似地，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，首先我们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（在本例中为人名）。在下一次迭代中，如果 Javascript 识别到键并且键的值不是未定义的，我们只需将 total_due 值添加到当前键值。

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;
    }
})

如何遍历 javascript 对象并在新对象中求和

How to loop through a javascript object and sum amounts in a new object

javascript

object

foreach-loop-container