如何防止对象在将两者相加时转换为字符串？答案

【问题标题】：How can I prevent object to get converted to string while adding both together?如何防止对象在将两者相加时转换为字符串？
【发布时间】：2019-03-06 13:44:53
【问题描述】：

我正在尝试编写一个逻辑来修改包含列表的数组的对象。例如：

    [
        {
            "S.N.": "1",
            "ITEM": "CIGARETTES",
            " QUANTITY SOLD ": " 3,603,221 ",
            "UNIT OF MEASURE": "CARTONS"
        },
        {
            "S.N.": "2",
            "ITEM": "LIQUOR",
            " QUANTITY SOLD ": " 5,680,586 ",
            "UNIT OF MEASURE": "BOTTLES"
        },
        {
            "S.N.": "3",
            "ITEM": "BEER",
            " QUANTITY SOLD ": " 7,581,446 ",
            "UNIT OF MEASURE": "CANS"
        }]

这样我会得到如下的最终结果：

    "CIGARETTES": {
            "S.N.": "1",
            "ITEM": "CIGARETTES",
            "QUANTITY": " 3,603,221 ",
            "UNIT": "CARTONS"
        },
        "LIQUOR": {
            "S.N.": "2",
            "ITEM": "LIQUOR",
            "QUANTITY": " 5,680,586 ",
            "UNIT": "BOTTLES"
        },
        "BEER": {
            "S.N.": "3",
            "ITEM": "BEER",
            "QUANTITY": "7,581,446 ",
            "UNIT": "CANS"
        }

我希望 ITEM 名称显示在上面给出的对象之前。我的逻辑如下：

    var callMe = function(){
    var newJson = json.map(function(item){
        var newItem = JSON.stringify(JSON.parse(item));
        newItem = item.ITEM + ':' + {item};
        return console.log(newItem)
    })
}

当我控制它时，我会收到以下信息：

 CIGARETTES:[object Object]
 LIQUOR:[object Object]
 BEER:[object Object]
 GOLD:[object Object]
 WATCHES:[object Object]

请告诉我如何阻止对象转换为字符串。

【问题讨论】：

这个：newItem = item.ITEM + ':' + {item}; 是关键问题。你不能像那样组合对象。
newItem = {[item.ITEM]: JSON.stringify(item)}

标签： javascript string object

【解决方案1】：

似乎对 JSON 是什么（Javascript 对象表示法）存在误解。它只是正在发送的数据的格式。

您正在使用的只是一个数组/对象。

你不应该修改一个字符串化的对象来添加数据。处理对象本身，然后对其进行字符串化。

const data=[{"S.N.":"1","ITEM":"CIGARETTES"," QUANTITY SOLD ":" 3,603,221 ","UNIT OF MEASURE":"CARTONS"},{"S.N.":"2","ITEM":"LIQUOR"," QUANTITY SOLD ":" 5,680,586 ","UNIT OF MEASURE":"BOTTLES"},{"S.N.":"3","ITEM":"BEER"," QUANTITY SOLD ":" 7,581,446 ","UNIT OF MEASURE":"CANS"}]

const res = data.reduce((a,c)=>{
  a[c.ITEM] = c;
  return a;
}, {});

console.log(res);

//then JSON.stringify res

非缩减版：

const data=[{"S.N.":"1","ITEM":"CIGARETTES"," QUANTITY SOLD ":" 3,603,221 ","UNIT OF MEASURE":"CARTONS"},{"S.N.":"2","ITEM":"LIQUOR"," QUANTITY SOLD ":" 5,680,586 ","UNIT OF MEASURE":"BOTTLES"},{"S.N.":"3","ITEM":"BEER"," QUANTITY SOLD ":" 7,581,446 ","UNIT OF MEASURE":"CANS"}]

const res = {};
for(let i = 0; i < data.length; i++){
  res[data[i].ITEM] = data[i];
}

console.log(res);

//then JSON.stringify res

【讨论】：

谢谢，@kemicofa :) 一种实现我想要的非常紧凑的方式 :)

【解决方案2】：

您可以使用reduce 进行转换

const   x = [
        {
            "S.N.": "1",
            "ITEM": "CIGARETTES",
            " QUANTITY SOLD ": " 3,603,221 ",
            "UNIT OF MEASURE": "CARTONS"
        },
        {
            "S.N.": "2",
            "ITEM": "LIQUOR",
            " QUANTITY SOLD ": " 5,680,586 ",
            "UNIT OF MEASURE": "BOTTLES"
        },
        {
            "S.N.": "3",
            "ITEM": "BEER",
            " QUANTITY SOLD ": " 7,581,446 ",
    }];
    
    const y = x.reduce(function(acc, item){
	acc[item.ITEM]= item;
	return acc;
}, {})

console.log(y);

【讨论】：

【解决方案3】：

遍历数组并将每个添加到一个对象中：

const items = [{
    "S.N.": "1",
    "ITEM": "CIGARETTES",
    " QUANTITY SOLD ": " 3,603,221 ",
    "UNIT OF MEASURE": "CARTONS"
  },
  {
    "S.N.": "2",
    "ITEM": "LIQUOR",
    " QUANTITY SOLD ": " 5,680,586 ",
    "UNIT OF MEASURE": "BOTTLES"
  },
  {
    "S.N.": "3",
    "ITEM": "BEER",
    " QUANTITY SOLD ": " 7,581,446 ",
    "UNIT OF MEASURE": "CANS"
  }
]

const output = {}

items.forEach(i => {
  output[i.ITEM] = i
})

console.log(output)

【讨论】：

非常感谢！这真的很有帮助:) :) :)