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社区首页 >问答首页 >从JSON数组中删除重复的对象

问从JSON数组中删除重复的对象
EN

Stack Overflow用户
提问于 2014-05-07 10:47:12
回答 17查看 122.9K关注 0票数 41

我有一个看起来像这样的数组：

代码语言：javascript
复制
var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

我需要删除重复项，这样就可以保留下面这样的内容：

代码语言：javascript
复制
var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

我尝试过安装underscore.js和使用._uniq，但似乎只有在对象中出现单个key:value对时才有效。我似乎不能让它在多个键上工作。

当我尝试这样的事情时：

代码语言：javascript
复制
var uniqueStandards = _.uniq(standardsList, function(item, key, Domain){
    return item.Domain;
});

我只得到前三个唯一的值(每个年级一个)。但我需要跨年级和领域的所有唯一值。有没有一种简单的方法将两个键都提供给_.uniq函数？

最终，我需要一个列表，将每个唯一的等级作为标题，将唯一的域作为列表项传递到HTML页面。我可能做错了，所以如果有更简单的方法来实现最终目标，我对想法持开放态度。

提前感谢！

编辑：得到了一些很好的回应，并想澄清我的最终目标是什么。我正在尝试用HTML创建表单的一系列列表：

代码语言：javascript
复制
<div>
    <h3>Math K</h3>
    <li>Counting & Cardinality</li>
    <li>Geometry</li>
</div>
<div>
    <h3>Math 1</h3>
    <li>Counting & Cardinality</li>
    <li>Orders of Operation</li>
</div>
<div>
    <h3>Math 2</h3>
    <li>Geometry</li>
</div>

我最初的想法是创建一个数组，并使用$("#divid").append(array)将其推入页面上的<div>元素中

javascript
jquery
underscore.js
EN

回答 17

Stack Overflow用户

回答已采纳

发布于 2014-05-07 11:30:31

最终，我需要一个列表，每个唯一的等级作为标题和唯一的域作为列表项目，以传递到

页面。我可能做错了，所以如果有更简单的方法来实现最终目标，我对想法持开放态度。

因此，您实际上并不需要您所要求的格式的输出数组。

在这种情况下，我会用一个非常简单有效的解决方案直接切入正题：

代码语言：javascript
复制
var grades = {};
standardsList.forEach( function( item ) {
    var grade = grades[item.Grade] = grades[item.Grade] || {};
    grade[item.Domain] = true;
});

console.log( JSON.stringify( grades, null, 4 ) );

生成的grades对象为：

代码语言：javascript
复制
{
    "Math K": {
        "Counting & Cardinality": true,
        "Geometry": true
    },
    "Math 1": {
        "Counting & Cardinality": true,
        "Orders of Operation": true
    },
    "Math 2": {
        "Geometry": true
    }
}

关于这种方法的一个有趣的事情是它非常快。请注意，与其他需要多次传递的解决方案不同，它只对输入数组进行一次传递(无论是您自己编写还是由_.uniq()为您完成)。对于少数项目，这并不重要，但对于较大的列表，最好记住这一点。

有了这个对象，您现在就拥有了运行任何代码或生成任何其他所需格式所需的一切。例如，如果您确实需要您提到的确切的数组输出格式，则可以使用：

代码语言：javascript
复制
var outputList = [];
for( var grade in grades ) {
    for( var domain in grades[grade] ) {
        outputList.push({ Grade: grade, Domain: domain });
    }
}

JSON.stringify( outputList, null, 4 );

这将记录以下内容：

代码语言：javascript
复制
[
    {
        "Grade": "Math K",
        "Domain": "Counting & Cardinality"
    },
    {
        "Grade": "Math K",
        "Domain": "Geometry"
    },
    {
        "Grade": "Math 1",
        "Domain": "Counting & Cardinality"
    },
    {
        "Grade": "Math 1",
        "Domain": "Orders of Operation"
    },
    {
        "Grade": "Math 2",
        "Domain": "Geometry"
    }
]

Rai在评论中询问这行代码是如何工作的：

代码语言：javascript
复制
var grade = grades[item.Grade] = grades[item.Grade] || {};

这是一种常见的习惯用法，用于获取对象属性或在缺少属性时提供默认值。请注意，=分配是按从右到左的顺序完成的。因此我们可以从字面上将其转换为使用if语句和temp变量：

代码语言：javascript
复制
// Fetch grades[item.Grade] and save it in temp
var temp = grades[item.Grade];
if( ! temp ) {
    // It was missing, so use an empty object as the default value
    temp = {};
}
// Now save the result in grades[item.Grade] (in case it was missing)
// and in grade
grades[item.Grade] = temp;
var grade = temp;

您可能会注意到，在grades[item.Grade]已经存在的情况下，我们将获取刚刚获取的值并将其存储回相同的属性中。当然，这是不必要的，如果您像这样编写代码，您可能不会这样做。相反，您可以将其简化：

代码语言：javascript
复制
var grade = grades[item.Grade];
if( ! grade ) {
    grade = grades[item.Grade] = {};
}

这将是一种完全合理的方式来编写相同的代码，而且效率也更高。它还为您提供了一种比||习惯用法所依赖的“真实性”更具体的测试方法。例如，您可能希望使用if( grade === undefined )而不是if( ! grade )。

票数 18
EN

Stack Overflow用户

发布于 2014-05-07 11:12:49

代码语言：javascript
复制
function arrUnique(arr) {
    var cleaned = [];
    arr.forEach(function(itm) {
        var unique = true;
        cleaned.forEach(function(itm2) {
            if (_.isEqual(itm, itm2)) unique = false;
        });
        if (unique)  cleaned.push(itm);
    });
    return cleaned;
}

var standardsList = arrUnique(standardsList);

这将返回

代码语言：javascript
复制
var standardsList = [
    {"Grade": "Math K", "Domain": "Counting & Cardinality"},
    {"Grade": "Math K", "Domain": "Geometry"},
    {"Grade": "Math 1", "Domain": "Counting & Cardinality"},
    {"Grade": "Math 1", "Domain": "Orders of Operation"},
    {"Grade": "Math 2", "Domain": "Geometry"}
];

这就是你想要的？

票数 28
EN

Stack Overflow用户

发布于 2017-11-16 01:06:39

我知道已经有很多答案了，但对于复杂的json结构，对我来说最好的答案是：

​

代码语言：javascript
复制
var arr = [{ "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RWCW", "desc": "WEST", "code": "RWCW", "level": 0, "save": "RWCW : WEST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RCSW", "desc": "SOUTHWEST", "code": "RCSW", "level": 0, "save": "RCSW : SOUTHWEST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RCNW", "desc": "MIDWEST", "code": "RCNW", "level": 0, "save": "RCNW : MIDWEST", "attribute1": "", "attribute2": "" }, { "State": "RSCW", "desc": "SOUTHEAST", "code": "RSCW", "level": 0, "save": "RSCW : SOUTHEAST", "attribute1": "", "attribute2": "" }, { "State": "RECW", "desc": "NORTHEAST", "code": "RECW", "level": 0, "save": "RECW : NORTHEAST", "attribute1": "", "attribute2": "" }];

var clean = arr.filter((arr, index, self) =>
    index === self.findIndex((t) => (t.save === arr.save && t.State === arr.State)))

console.log(clean);

​

您可以直接在chrome浏览器控制台进行尝试，并根据需要进行编辑。

我希望这对某些人有帮助。

票数 27
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/23507853

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