检查对象数组是否具有> 1个属性值！== undefined

Question

我有一个这样的对象数组：

var array = [
  {"name": "one", "value": .33},
  {"name": "one", "value": .54},
  {"name": "one", "value": undefined},

  {"name": "two", "value": .3},
  {"name": "two", "value": undefined},
  {"name": "two", "value": undefined},

  {"name": "three", "value": undefined},
  {"name": "three", "value": undefined},
  {"name": "three", "value": undefined},
];

我需要能够看到是否有任何唯一名称（一个/两个/三个）在其“值”属性中只有一个数字。 因此，在此示例中，答案为Yes，因为“two”的值属性为：.3，undefined，undefined。

我有一个很好的方法将唯一的“名称”字段放入一个数组：

function Names(a) {
  var temp = {};
  for (var i = 0; i < a.length; i++)
    temp[a[i].name] = true;
  var r = [];
  for (var k in temp)
    r.push(k);
  return r;
}

nameArray = Names(array);

但是当我开始寻找实际的循环时，我开始感到困惑。 只是把它写出来我会认为它会像：

var count = 0;
for (objects with name == i){
  if (isNaN(value) == false){
    count++
    if(count > 1) {
      return true;
    }
  }
}

当然，这是伪代码，甚至可能不是正确的方向。 任何帮助表示赞赏，感谢阅读！

Answer 1

你可以是为每一个独特的名字数字值的计数创建对象，然后检查是否有名字的数是1， some和将返回true/false

 var array = [{"name":"one","value":0.33},{"name":"one","value":0.54},{"name":"one"},{"name":"two","value":0.3},{"name":"two"},{"name":"two"},{"name":"three"},{"name":"three"},{"name":"three"}], obj = {} array.forEach(function(e) { if(!obj[e.name]) obj[e.name] = 0; if(typeof e.value == 'number') obj[e.name]+=1; }); var result = Object.keys(obj).some(e => { return obj[e] == 1}); console.log(result) 

Answer 2

如果您不能保证它们将按照阵列中的名称进行排序，那么Nenad有最好的答案。

但是，如果订单得到保证，您可以编写如下函数：

 //Should be false var array1 = [{"name":"one","value":0.33}]; //Should be false var array2 = [{"name":"one","value":0.33},{"name":"one","value":0.54}]; //Should be false var array3 = [{"name":"one","value":0.33},{"name":"one","value":0.54},{"name":"one","value":undefined}]; //Should be true - middle sequence contains one value var array4 = [{"name":"one","value":0.33},{"name":"one","value":0.54},{"name":"one"},{"name":"two"},{"name":"two","value":0.3},{"name":"two"},{"name":"three"},{"name":"three"},{"name":"three"}]; //Should be true - last sequence contains one value var array5 = [{"name":"one","value":0.33},{"name":"one","value":0.54},{"name":"one"},{"name":"two"},{"name":"two","value":0.3},{"name":"two", "value":0.3},{"name":"three"},{"name":"three"},{"name":"three","value":0.3}]; function containsUniqueValueForUniqueName(entry, index) { //So you can see in console how it short circuits the loop. console.log("Checking entry", entry); //If the value is a number, then increase the last count. if (!isNaN(entry.value)) { this.lastName = entry.name; this.lastCount += 1; } //When the lastName changes, or if its the last entry in the array, check if lastCount was 1. If yes, then exit true. if (this.lastName !== entry.name || index === array1.length - 1) { if (this.lastCount === 1) return true; //If its not 1, then we need to reset the count to 0. this.lastCount = 0; } return false; } var array1Result = array1.some(containsUniqueValueForUniqueName, {}); var array2Result = array2.some(containsUniqueValueForUniqueName, {}); var array3Result = array3.some(containsUniqueValueForUniqueName, {}); var array4Result = array4.some(containsUniqueValueForUniqueName, {}); var array5Result = array5.some(containsUniqueValueForUniqueName, {}); console.log('array1', array1Result); console.log('array2', array2Result); console.log('array3', array3Result); console.log('array4', array4Result); console.log('array5', array5Result); 

一旦遇到一个只有1个值的连续集，它就会退出循环。

在一个非常大的数组上，可以为您节省相当多的迭代次数。 同样，它要求您的数据按名称预先排序。 所以，如果你从网络服务或类似的东西中得到它，那么我建议使用这个答案。

Answer 3

如果你想考虑使用lodash （这里是一个jsbin示例 ）：

var array = [
  {"name": "one", "value": 0.33},
  {"name": "one", "value": 0.54},
  {"name": "one", "value": undefined},

  {"name": "two", "value": 0.3},
  {"name": "two", "value": undefined},
  {"name": "two", "value": undefined},

  {"name": "three", "value": undefined},
  {"name": "three", "value": undefined},
  {"name": "three", "value": undefined},
];

// groups objects by the key `name`
array = _.groupBy(array, function(obj) {
  return obj.name;
});

// gets the counts for each `name` of `value` properties that are numbers
array = _.mapValues(array, function(arr) {
  return arr.filter(function(obj) {
     return _.isNumber(obj.value);
  }).length;
});

console.log(array);

这将输出：

{
  one: 2,
  three: 0,
  two: 1
}

这告诉您名称为one对象有2个value数字的value ， three有0个value数字， two有1个value数字。