如何停止为值重复键

Question

我有一个数组序列号。它可能看起来像这样。

lot: 1  Serial: 2
lot: 1  Serial: 3
lot: 1  Serial: 4

... 等等。或者看起来像

lot: 1  Serial: 5
lot: 1  Serial: 9
lot: 8  Serial: 2
lot: 8  Serial: 4

var dictSerials = []
if (serialNumbers.length > 0) 
    for (var i of serialNumbers) {
        dictSerials.push({
            key: i.value.lot,
            value: i.value.serial
        })
    }

这是我试图用来让事情正常进行的方法，但这会为列出的每个项创建一个键和值。我希望我的结果是这样的对象：

Key: 1  Value: 2, 3, 4, 5, 9
Key: 8  Value: 2, 4

谁能帮我解决这个问题？谢谢！

Answer 1

满足您要求的另一种方法是使用函数reduce 对键和值进行分组。

let array = [{lot: 1, Serial: 2},{lot: 1, Serial: 3},{lot: 1, Serial: 4},{lot: 1, Serial: 5},{lot: 1,Serial: 9},{lot: 8,Serial: 2},{lot: 8,Serial: 4}],
    result = Object.values(array.reduce((a, c) => {
      (a[c.lot] || (a[c.lot] = {Key: c.lot, Value: []})).Value.push(c.Serial);
      return a;
    }, {}));
    
console.log(result);

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Answer 2

不确定是否有更好/更简单的方法，但可以这样做：-

 var array = [{
      name: "foo1",
      value: "val1"
    }, {
      name: "foo1",
      value: ["val2", "val3"]
    }, {
      name: "foo2",
      value: "val4"
    }];

    var output = [];

    array.forEach(function(value) {
      var existing = output.filter(function(v, i) {
        return v.name == value.name;
      });
      if (existing.length) {
        var existingIndex = output.indexOf(existing[0]);
        output[existingIndex].value = output[existingIndex].value.concat(value.value);
      } else {
        if (typeof value.value == 'string')
          value.value = [value.value];
        output.push(value);
      }
    });

    console.dir(output);

Answer 3

这是一个使用两个 forEach 循环的简单方法：

const arr = [
  {lot : 1, Serial : 2},
  {lot : 1, Serial : 3},
  {lot : 1, Serial : 4},
  {lot : 1, Serial : 5},  
  {lot : 1, Serial : 9},
  {lot : 8, Serial : 2},
  {lot : 8, Serial : 4}
]

let grouped = [],
  result = [];

arr.forEach((e) => {
  (result[e.lot] || (result[e.lot] = [])).push(e.Serial)
})

result.forEach((e, i) => {
  grouped.push({
    "key": i,
    "value": e.join(',')
  })
});

console.log(grouped)

Answer 4

您可以为此使用Map。

var serialNumbers = [
  {value:{lot:1, serial: 2}},
  {value:{lot:1, serial: 3}},
  {value:{lot:1, serial: 4}},
  {value:{lot:1, serial: 5}},
  {value:{lot:1, serial: 9}},
  {value:{lot:8, serial: 2}},
  {value:{lot:8, serial: 4}},
 ];

var dictSerials = new Map();
if (serialNumbers.length > 0) {
  for (var i of serialNumbers) {
      if(!dictSerials.has(i.value.lot)) {
        dictSerials.set(i.value.lot, [i.value.serial]);        
      } else {
        var v = dictSerials.get(i.value.lot);
        v.push(i.value.serial);
        dictSerials.set(i.value.lot, v);        
      }      
  }
}
//Output
for (var [key, value] of dictSerials.entries()) {
  console.log("Key: " + key + " Value: " + value.join(","));
}

Answer 5

function getDictSerials(serialNumbers) {

    var dictSerials = {};

    if (serialNumbers.length > 0) {
        for (let i of serialNumbers) {
            let lot = i.lot;
            let serial = i.serial;

            if (!dictSerials[lot]) { // If the key isn't found - intiate an array
                dictSerials[lot] = [];
            }

            dictSerials[lot].push(serial) // push the serial to the corresponding lot
        }
    }

    return dictSerials;
}

let serialNumbers = [
    {lot : 1, serial : 2},
    {lot : 1, serial : 3},
    {lot : 1, serial : 4},
    {lot : 1, serial : 5},
    {lot : 1, serial : 9},
    {lot : 8, serial : 2},
    {lot : 8, serial : 4}
];

let desiredObj =  {
    dictSerials: getDictSerials(serialNumbers)
}

JSON.stringify(desiredObj); // {"dictSerials":{"1":[2,3,4,5,9],"8":[2,4]}}

Answer 6

var dictSerials = []
if (serialNumbers.length > 0) {
    for (var i of serialNumbers) {

      if(!dictSerials[i.value.lot]){
          dictSerials[i.value.lot] = [];
      }

       dictSerials[i.value.lot][] = i.value.serial;
    }
}

上面的代码会将值添加到它们对应的键中。