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我有一个包含objectiveDetail 对象的javascript 数组。

objectiveDetails[]

这里我添加了一个新的objectiveDetail：

var emptyObjectiveDetail = {
  "number": formData.objectiveDetails.length +1, // I want to change this !
  "text": "", 
  "response": false, 
  "objectiveId": formData.objectiveId
};
objectiveDetails.push(emptyObjectiveDetail);

我怎样才能使我分配给 emptyObjectDetail 字段的数字等于数组中objectiveDetail对象当前使用的最大数字。

换句话说，如果我有三个objectiveDetail对象，其中“数字”字段设置为1、4和5，那么当我添加一个新对象时，我想用数字6而不是数组的长度+ 1来添加它

我也对使用 _underscore 感兴趣，并想知道是否有一种使用下划线和 javascript 的好方法

4

5 回答 5

2

试试下面的示例。

基本思想是使用该函数创建一个仅包含数组number值的虚拟一维数组，然后用于在该虚拟一维数组中查找最大值。objectiveDetails.mapMath.max

var maxNum  = Math.max.apply(Math,objectiveDetails.map(function(o){return o.number;}));
var emptyObjectiveDetail = {
    "number": maxNum+1,
  "text": "", 
  "response": false, 
  "objectiveId": 123
};
objectiveDetails.push(emptyObjectiveDetail);
于 2013-08-10T09:14:06.887 回答
1

如果我正确理解了这个问题并且formData.objectiveDetails只包含数值，我认为您可以使用它Math.max来确定最大值：

var emptyObjectiveDetail = {
  "number": Math.max.apply(null,formData.objectiveDetails) + 1,
  // etc.
};
于 2013-08-10T09:03:05.640 回答
0

你可以试试

var emptyObjectiveDetail = {
  "number": objectiveDetails[objectiveDetails.length-1].number + 1, // I want to change this !
  "text": "", 
  "response": false, 
  "objectiveId": formData.objectiveId
};
objectiveDetails.push(emptyObjectiveDetail);

它将使键“数字”的值等于最后输入的数字。

但是，要真正找到最大的，您必须遍历所有值并找到最大的“数字”。

于 2013-08-10T08:22:54.813 回答
0

这是我的建议：

// create an empty array
var objectiveDetails = [];
// set the current highestNumber to 0
objectiveDetails.highestNumber = 0;
// add a custom method to add an objectiveDetail
objectiveDetails.add = function(objectiveDetail) {
    // if objectiveDetail is not given make an empty object
    objectiveDetail = objectiveDetail ? objectiveDetail : {};
    // if objectiveDetail.number is not given give it highestNumber+1
    if (!objectiveDetail.number) {
        objectiveDetail.number = objectiveDetails.highestNumber + 1;
    }
    // check if highestNumber is still the highest
    if (objectiveDetail.number > objectiveDetails.highestNumber) {
        objectiveDetails.highestNumber = objectiveDetail.number;
    }
    // add objectiveDetail to array
    objectiveDetails.push(objectiveDetail);
}

例子：

var emptyObjectiveDetail = {
  "number": 3,
  "text": "", 
  "response": false, 
  "objectiveId": 412
};
objectiveDetails.add(emptyObjectiveDetail);

var emptyObjectiveDetail = {
  "number": 2,
  "text": "", 
  "response": false, 
  "objectiveId": 413
};
objectiveDetails.add(emptyObjectiveDetail);

var emptyObjectiveDetail = {
  "text": "", 
  "response": false, 
  "objectiveId": 414
};
objectiveDetails.add(emptyObjectiveDetail);

var emptyObjectiveDetail = {
  "number": objectiveDetails.highestNumber+1,
  "text": "", 
  "response": false, 
  "objectiveId": 414
};
objectiveDetails.add(emptyObjectiveDetail);

console.log(objectiveDetails);
于 2013-08-10T08:33:28.533 回答
0

我相信除了已经建议的方法之外，还有其他两种方法：

1）（最有效）：将值存储在一个数字中（可能作为全局变量或作为类的变量）。在添加对象时不断更新它。添加新对象时，请检查此编号并相应地添加对象。

优点：计算效率最高。添加新对象时无需遍历所有对象。

2）（优化我相信）：好的，这里使用下划线，我相信它是优化的：D

var maxNum = _.max(objectiveDetails,function(objectiveDetail){return objectiveDetail.number;});
var emptyObjectiveDetail = {
    "数字": maxNum+1,
  “文本”： ””，
  “响应”：错误，
  “目标标识”：123
};
objectDetails.push(emptyObjectiveDetail);

优点：使用针对此类内容进行了优化的库。

希望有帮助:)

于 2013-08-10T09:57:40.383 回答