Question

我已经说过，标签为<textarea>的5个文本框。如何随机选择50％的文本框？每个文本框都有不同的ID。例如：

<textarea id = "text1" name= "name1"></textarea>
<textarea id = "text2" name= "name2"></textarea>
<textarea id = "text3" name= "name3"></textarea>
<textarea id = "text4" name= "name4"></textarea>
<textarea id = "text5" name= "name5"></textarea>

我可以在ID上使用某种随机函数吗？

Answer 1

使用Math.random()方法生成随机索引。

// get all textarea eleemnts as an array
var $t = $('textarea[id^="text"]').get();

// iterate upto half length
for (var i = 0, len = $t.length / 2; i < len; i++) {
  // generate random index and remove it from collection
  // where element can be remove using splice method
  // and which returns an array of removed elements       
  // get the elment from that array and update the value or do whatever you are trying to achieve
  $t.splice(Math.floor(Math.random() * $t.length), 1)[0].value = i;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea id="text1" name="name1"></textarea>
<textarea id="text2" name="name2"></textarea>
<textarea id="text3" name="name3"></textarea>
<textarea id="text4" name="name4"></textarea>
<textarea id="text5" name="name5"></textarea>

Answer 2

以有效的方式查看How to get n no elements randomly from an array，从阵列中选择n随机元素（这将返回唯一元素）。调整此解决方案，您可以执行以下操作：

// https://stackoverflow.com/questions/19269545/how-to-get-n-no-elements-randomly-from-an-array
function getRandom(arr, n) {
    var result = new Array(n),
        len = arr.length,
        taken = new Array(len);
    if (n > len)
        throw new RangeError("getRandom: more elements taken than available");
    while (n--) {
        var x = Math.floor(Math.random() * len);
        result[n] = arr[x in taken ? taken[x] : x];
        taken[x] = --len;
    }
    return result;
}

var textareas = $('textarea');
var randomTextareas = getRandom(textareas, textareas.length / 2);
randomTextareas.forEach(function(textArea) { 
  $(textArea).prop('value', 'hello');
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea id="text1" name= "name1"></textarea>
<textarea id="text2" name= "name2"></textarea>
<textarea id="text3" name= "name3"></textarea>
<textarea id="text4" name= "name4"></textarea>

如何在Jquery中选择随机文本框？

2 个答案: