Javascript数组排序具有键值条件的唯一对象

Question

我有一个数组

"datawithisNew": [
        {
            "exam_name": "MPSC",
            "isNew": false
        },
        
        {
            "exam_name": "MPSC",
            "isNew": true
        },
        {
            "exam_name": "UPSC",
            "isNew": false
        },
      
        {
            "exam_name": "RAILWAY",
            "isNew": false
        },
        {
            "exam_name": "RAILWAY",
            "isNew": false
        }]

我正在尝试获得具有唯一 exam_name 的结果，这样如果 exam_name 至少有 1 个 isNew 键为真，则结果对象数组也具有唯一的 exam_name 值，则结果对象应该具有isNew true 的属性，如果不是 false。 预期的结果 -

"datawithisNew": [
        {
            "exam_name": "MPSC",
            "isNew": true
        },

        {
            "exam_name": "UPSC",
            "isNew": false
        },
        {
            "exam_name": "RAILWAY",
            "isNew": false
        }]

我使用的代码是-

 var helper1 = {};
    var result2 = data12.reduce(function(r, o) {
    var key = o.exam_name ;
    
    if(!helper1[key]) {
      helper1[key] = Object.assign({}, o); // create a copy of o
      r.push(helper1[key]);
    } else {
      helper1[key].exam_name_rating += o.exam_name_rating;
    }
    return r;
  }, []);

但这只是返回唯一的exam_name 对象我还需要isNew 键，如果它至少出现一次true 对于exam_name 它应该有isNew:true 为真，否则isNew:false

Answer 1

您离实际解决方案不远，添加以下行可以解决您的问题：

helper1[key].isNew ||= o.isNew;

如果当前值是假的，||= 将分配一个变量或属性给一个值。

如果您不能使用 logical OR assignment (||=) 运算符，因为它是一个相当新的赋值运算符，您可以使用：

if (!helper1[key].isNew) helper1[key].isNew = o.isNew;

const data12 = [
  { "exam_name": "MPSC",    "isNew": false },
  { "exam_name": "MPSC",    "isNew": true  },
  { "exam_name": "UPSC",    "isNew": false },
  { "exam_name": "RAILWAY", "isNew": false },
  { "exam_name": "RAILWAY", "isNew": false },
];

var helper1 = {};
var result2 = data12.reduce(function(r, o) {
  var key = o.exam_name ;

  if(!helper1[key]) {
    helper1[key] = Object.assign({}, o); // create a copy of o
    r.push(helper1[key]);
  } else {
    helper1[key].exam_name_rating += o.exam_name_rating;
    helper1[key].isNew ||= o.isNew; // <- added this line
  }
  return r;
}, []);

console.log(result2);

由于示例数据不包含exam_name_rating 属性，因此它将丢失或设置为NaN 以获得结果。我假设此属性在您自己的数据中可用。

Answer 2

使用 JS Array.filter 过滤掉重复项

const datawithisNew = [{
    "exam_name": "MPSC",
    "isNew": false
  },

  {
    "exam_name": "MPSC",
    "isNew": true
  },
  {
    "exam_name": "UPSC",
    "isNew": false
  },

  {
    "exam_name": "RAILWAY",
    "isNew": false
  },
  {
    "exam_name": "RAILWAY",
    "isNew": false
  }
];

const uniqueItems = datawithisNew.filter((exam, index, self) => {
  return self.findIndex(e => exam.exam_name === e.exam_name) === index
}).map(exam => {
  if (!exam.isNew && datawithisNew.find(e => e.exam_name === exam.exam_name && e.isNew)) {
    exam.isNew = true;
  }
  return exam;

});



console.log(uniqueItems);

Answer 3

使用 datawithisNew 作为参数调用下面的函数

     function getUniqueExams(data){
let finalObjMap = { };
for(var i=0;i<data.length;i++){
let currentObj = data[i];
if(finalObjMap[currentObj["exam_name"]])
{
if(!finalObjMap[currentObj["isNew"]] && currentObj["isNew"])
    finalObjMap[currentObj["exam_name"]]["isNew"]=true;
}
else
{
    finalObjMap[currentObj["exam_name"]]={"isNew":currentObj["isNew"]};
}

}
let finalData=[];
Object.keys(finalObjMap).forEach((key)=>{
let tempExamObj  = { "exam_name": key , "isNew": finalObjMap[key]["isNew"]};
finalData.push(tempExamObj);

});
return finalData;
};

    var datawithisNew=[
            {
                "exam_name": "MPSC",
                "isNew": false
            },
            
            {
                "exam_name": "MPSC",
                "isNew": true
            },
            {
                "exam_name": "UPSC",
                "isNew": false
            },
          
            {
                "exam_name": "RAILWAY",
                "isNew": false
            },
            {
                "exam_name": "RAILWAY",
                "isNew": false
            }];
    console.log(getUniqueExams(datawithisNew));