从javascript中的数组中获取随机X项
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【中文标题】从javascript中的数组中获取随机X项【英文标题】:Get random X items from array in javascript 【发布时间】:2017-02-01 22:51:36 【问题描述】:我有以下使用测试数据的小提琴,我正在使用 $.each 查看数据
我可以循环遍历没有问题,但是我想循环遍历数据,然后从中随机获取3个对象。
任何提示或技巧都会有所帮助:
https://jsfiddle.net/inkedraskal/pah44qv6/
$.each(testData,function(x, blah)
//console.log(blah._id);
//this gets each objects id & picture, but I want to get 3 random objects, and their corresponding data
var activeValue = blah._id,
pictureValue = blah.picture;
var markUp = '';
markUp += activeValue + pictureValue;
console.log(markUp);
);
对于下面的问题,它们必须是唯一的**
【问题讨论】:
三个随机项必须是唯一的吗? 哦,好问题,是的,它们必须是独一无二的 只寻找使用$.each
的解决方案?有什么具体原因吗?您可以查看我的答案,如果可以,请告诉我。
【参考方案1】:
我们可以创建getRandomEntry()
函数,该函数将使用Math.random()
函数返回数组元素之一。我们将创建一个循环,每次迭代时都会随机输入。
function getRandomEntry()
return testData[Math.round(Math.random() * (testData.length - 1))];
for (var i=0; i<3; i++)
var entry = getRandomEntry();
console.log(entry._id, entry.picture);
如果您每次都需要一个唯一的条目。您可以将随机条目保存在单独的数组中,并检查新条目是否不完整。
var randomEntries = [];
function getRandomEntry()
return testData[Math.round(Math.random() * (testData.length - 1))];
function entryExists(entry)
return randomEntries.indexOf(entry) > -1;
for (var i=0; i<3; i++)
var entry;
do
entry = getRandomEntry();
while(entryExists(entry))
randomEntries.push(entry);
console.log(entry._id, entry.picture);
【讨论】:
这将无法满足他们需要是唯一的要求 编辑了答案。【参考方案2】:您可以使用如下递归函数。
请注意,此实现可防止结果中出现重复
function getRandomObjects(array,selected,needed)
/*
*@param array array The array to pull from
*@param selected array The array of results pulled so far
*@param needed int The number of results we want
*/
var length = array.length;
var num = Math.floor(Math.random() * length) + 1; // get random number in bounds of array
var exists=false; // make sure we didnt already pick this object
$.each(selected,function(i,obj)
if(obj.index==num)exists=true;
)
if(exists) getRandomObjects(array,selected,needed); // get a new one if this was a duplicate
else selected.push(array[num]);
if(selected.length!=needed) return getRandomObjects(array,selected,needed); // get another object if we need more
else return selected; // return the final result set
var testData = [
"_id": "57e5d1a90c4206b128cd8654",
"index": 0,
"guid": "1f3269fc-0822-4c5a-9c52-8055155b407e",
"isActive": true,
"balance": "$3,026.95",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a9a986ccb2f41cf7b9",
"index": 1,
"guid": "a6b726b6-6466-4e48-8697-1c6bd7b1c79e",
"isActive": true,
"balance": "$2,642.74",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a9f98f8b2f6880de32",
"index": 2,
"guid": "e7d736cc-19e0-4bcb-8d0a-4d17442d8cee",
"isActive": true,
"balance": "$3,341.64",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a9e40ded5b017e45cd",
"index": 3,
"guid": "64230ca8-05c0-4c39-a931-794172475a32",
"isActive": true,
"balance": "$2,196.13",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a90cc30be769a06d7c",
"index": 4,
"guid": "d6618b78-753a-4ad0-bc14-3687d0b99196",
"isActive": true,
"balance": "$1,611.62",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a92481a43f50607415",
"index": 5,
"guid": "35ec8186-9494-4f89-ab89-bed7f39872c3",
"isActive": true,
"balance": "$3,148.87",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a9164f17c558ba7ce1",
"index": 6,
"guid": "244970a0-1ce2-405a-8d69-c7903f9bf5eb",
"isActive": false,
"balance": "$3,758.13",
"picture": "http://placehold.it/32x32"
,
"_id": "57e5d1a95afde31c5cf592a8",
"index": 7,
"guid": "aa30c82d-dd2b-420c-8b30-7d66cec8d10b",
"isActive": true,
"balance": "$1,311.40",
"picture": "http://placehold.it/32x32"
]
var randomObjects=getRandomObjects(testData,[],3);
console.log(randomObjects);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
【讨论】:
【参考方案3】:下面的 sn-p 中的函数获取一个数组和一个数量 (X) 的项,并返回一个新数组,其中包含来自原始数组的 X 个唯一随机项:
function getRandomItems(arr, items)
var ret = [];
var indexes = [];
var arr_length = arr.length;
// If we don't have enough items to return - return the original array
if (arr_length < items)
return arr;
while (ret.length < items)
i = Math.floor(Math.random() * arr_length);
if (indexes.indexOf(i) == -1)
indexes[indexes.length] = i;
ret[ret.length] = arr[i];
return ret;
arr = ['a', 'b', 'c', 'd', 'e']
console.log(getRandomItems(arr, 2))
如果您想在代码中的每个 Array
上使用它作为“本机”函数,也可以将函数添加到 Array.prototype
:
Array.prototype.getRandomItems = function(items)
var ret = [];
var indexes = [];
var arr_length = this.length;
// If we don't have enough items to return - return the original array
if (arr_length < items)
return this;
while (ret.length < items)
i = Math.floor(Math.random() * arr_length);
if (indexes.indexOf(i) == -1)
indexes[indexes.length] = i;
ret[ret.length] = this[i];
return ret;
arr1 = ['a', 'b', 'c', 'd', 'e']
arr2 = ['aaa', 'bbb', 'ccc', 'ddd', 'eee']
console.log(arr1.getRandomItems(1))
console.log(arr1.getRandomItems(2))
console.log(arr2.getRandomItems(3))
console.log(arr2.getRandomItems(4))
【讨论】:
【参考方案4】:你可以这样做
var items = [1, 2, 3, 4, 5];
var newItems = [];
for(var i = 0; i < 3; i++)
var idx = Math.floor(Math.random() * items.length);
newItems.push(items[idx]);
items.splice(idx, 1);
console.log(newItems);
【讨论】:
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