如何使用唯一元素创建数组（即删除重复项）？

I have this code:

我有这个代码：

var ar = [10,7,8,3,4,7,6];

function isin(n,a){
  for (var i=0;i<a.length;i++){
    if (a[i]== n) {
      var b = true;
      return b;
    } else {
      var c = false;
      return c;
   }
  }
}

function unique(a){
  var arr = [];
  for (var i=0;i<a.length;i++){
    if (!isin(a[i],arr)){
      arr.push(a[i]);
    }
  }

 return arr;
}

alert(unique(ar));

In this code, I try to create new unique array (without duplicates) out of the original one. But I still get the original array! Where's my mistake?

在这段代码中，我尝试从原始数组创建新的唯一数组（没有重复）。但我仍然得到原始阵列！哪里是我的错？

13 个解决方案

#1

Using a plain array and returning the keys of associative array (containing only the "unique" values from given array) is more efficient:

使用普通数组并返回关联数组的键（仅包含给定数组中的“唯一”值）更有效：

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

$(document).ready(function() {
    var arr = [10, 7, 8, 3, 4, 3, 7, 6];
    var noDupes = ArrNoDupe(arr);
    $("#before").html("Before: " + arr.join(", "));
    $("#after").html("After: " + noDupes.join(", "));
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="before"></div>
<div id="after"></div>

Note: The function does not preserve the order of the items, so if this is important use different logic.

注意：该函数不保留项的顺序，因此如果这很重要，请使用不同的逻辑。

As of IE9 and on all other modern browsers (e.g. Chrome, Firefox) this can become even more efficient by using the Object.keys() method:

从IE9和所有其他现代浏览器（例如Chrome，Firefox）开始，使用Object.keys（）方法可以提高效率：

function ArrNoDupe(a) {
    var temp = {};
    for (var i = 0; i < a.length; i++)
        temp[a[i]] = true;
    return Object.keys(temp);
}

$(document).ready(function() {
    var arr = [10, 7, 8, 3, 4, 3, 7, 6];
    var noDupes = ArrNoDupe(arr);
    $("#before").html("Before: " + arr.join(", "));
    $("#after").html("After: " + noDupes.join(", "));
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="before"></div>
<div id="after"></div>

_{Thanks wateriswet for bringing this to my attention. :)}

感谢wateriswet引起我的注意。 :)

#2

Or for those looking for a one-liner (simple and functional):

或者对于那些寻找单线程（简单且功能齐全）的人：

var a = ["1", "1", "2", "3", "3", "1"];
var unique = a.filter(function(item, i, ar){ return ar.indexOf(item) === i; });

#3

You could use the new native new Set(list) object in ES6/ES2015. (i.e. Babel, Typescript, or those lucky enough that all target browsers support ES2015).

您可以在ES6 / ES2015中使用新的本机新Set（list）对象。（即Babel，Typescript，或者幸运的是所有目标浏览器都支持ES2015）。

// I never use this, because it's an iterator, not an array
let s = new Set(list);

or, if you want to chain to array helpers use the new ... spread operator in ES6/ES2015 to spread it into an array:

或者，如果要链接到数组助手，请使用ES6 / ES2015中的新... spread运算符将其扩展到数组中：

const unique = (list) => {
  return [...new Set(list)];
}

You need an array to chain methods like sort():

你需要一个数组链接sort（）方法：

const convertText = (textToConvert) => {
  let list = unique(textToConvert.split(/\r?\n/g))
    .sort() // this will error if using uniqueAsIterator() version...
    .filter(x => x != "NULL");
  return list;
}

#4

Edit: note the warning by Daniel. Considering that, and what the official docs say (below), maybe using this is not a great idea after all!

编辑：注意丹尼尔的警告。考虑到这一点，以及官方文档的说法（下文），也许使用它毕竟不是一个好主意！

If you happen to use jQuery, its unique() function does this:

如果你碰巧使用jQuery，它的unique（）函数会这样做：

var ar = [1, 2, 1, 2, 2, 3];    
ar = $.unique(ar);
console.log(ar);  // [3, 2, 1]

The documentation says:

文件说：

Note that this only works on arrays of DOM elements, not strings or numbers.

请注意，这仅适用于DOM元素的数组，而不适用于字符串或数字。

...but when I tested this with jQuery 1.9.1, it does work for strings and numbers too. Anyway, double-check that it works, especially if using older jQuery.

...但是当我用jQuery 1.9.1测试它时，它确实适用于字符串和数字。无论如何，仔细检查它是否有效，特别是如果使用旧的jQuery。

#5

In addition to usage of filter respond by Josh Mc, you can make it crazy shorter in es6 with arrow function utility;

除了使用Josh Mc的过滤器响应之外，你还可以使用箭头功能实用程序在es6中缩短它的速度;

const a = ["1", "1", "2", "3", "3", "1"];
let unique = a.filter((it, i, ar) => ar.indexOf(it) === i);
// unique = [1, 2, 3]

#6

Because your isin method returns true or false after examining the first element.

因为你的isin方法在检查第一个元素后返回true或false。

change it to this:

把它改成这个：

function isin(n,a){
  for (var i=0;i<a.length;i++){
    if (a[i]== n){
    return true;

    }
  }
  return false;
}

#7

You should use indexOf instead of your isIn function:

您应该使用indexOf而不是isIn函数：

function unique(a){
  var arr = [];
  for (var i=0;i<a.length;i++){
    if ( arr.indexOf(a[i]) == -1){
        arr.push(a[i]);
    }
}

#8

And with some ES5 fun...

有一些ES5的乐趣......

function uniqueArray(array) {
    var temp = array.reduce(function(previous, current) {
        previous[current] = true;
        return previous;
    }, {});

    return Object.keys(temp);
}

#9

Where's my mistake??

哪里是我的错？

Right here:

就在这儿：

... else {
      var c = false;
      return c;
   }

This causes the isin function to false if n doesn't match the first element in the array. The loop-body will always return a value before progressing to the next element.

如果n与数组中的第一个元素不匹配，则会导致isin函数为false。在进入下一个元素之前，循环体将始终返回一个值。

Remove the else-clause and move return false to the bottom of the method:

删除else子句并将return false移到方法的底部：

function isin(n,a){
    for (var i=0;i<a.length;i++) {
        if (a[i] == n)
            return true;

    return false;
}

Note that the isin method can be implemented immediately (or even replaced by) a call to indexOf.

请注意，isin方法可以立即执行（甚至替换为）对indexOf的调用。

#10

The way I did it was to use the array "backwards", so when I push to it I use the key instead of the value, like this:

我这样做的方法是使用“向后”的数组，所以当我按下它时，我使用键而不是值，如下所示：

var arr = [];
$('input[type=checkbox]', SearchResults).each( function() {
    if( $(this).is(':checked') )
        arr[ $(this).data('client_id') ] = true;
}

Then I look at the keys rather than the values.

然后我看看键而不是值。

#11

I know I'm somewhat late to answer this. But none of the answers have what I would do. I like using splice for this sort of thing. Here's a really simple script that'll do exactly what you need:

我知道我回答这个问题有点迟了。但是没有一个答案符合我的要求。我喜欢使用拼接来做这种事情。这是一个非常简单的脚本，它可以完全满足您的需求：

function unique(originalArray){
    var ar = originalArray.slice(0);//Make a copy of the array and store it in ar
    var i = ar.length;
    while(i--){  //Iterate through the array
        if(ar.indexOf(ar[i],i+1)>-1){  //If the array has a duplicate
            ar.splice(i,1);  //Remove that element!
        }
    }
    return ar; //Return the new, more unique array
}

#12

Based on the accepted answer. Here is a CoffeeScript equivalent:

根据接受的答案。这是CoffeeScript的等价物：

unique = (a) ->
  temp = {}
  for i in [0...a.length]
    temp[a[i]] = true
  r = []
  for k of temp
    r.push(k)
  return r

#13

I've done a similar search, I found this answer really good:

我做了类似的搜索，我发现这个答案非常好：

Unique values in an array [duplicate]

数组中的唯一值[重复]

You can re-use those function on other code. This is also good approach where it is compatible with many browsers.

您可以在其他代码上重用这些功能。这也是与许多浏览器兼容的好方法。

Cheer.

欢呼。

#1