动态添加/删除所需的属性 [英] add/remove required attribute dynamically

问题描述

我想添加/删除输入元素的必需属性.但不知何故它不起作用.

I want to add/remove the required attribute of an input element. But somehow it doesn't work.

如果罪犯车牌号文本字段为空，则应要求描述车辆文本字段.

If offender Plate# text field is empty, Describe vehicle text field should be required.

罪犯牌号:<input type="text" id="plate_num_id" name="plate_num" onblur="checkForRequired()"><br>

描述车辆:<textarea id="vehicle_desc_id" name="vehicle_desc"></textarea><br>

然后这是我的功能.

function checkForRequired() {

    var plateLength = document.getElementById("plate_num_id").value.length;

    if (plateLength < 1) {

        $("#vehicle_desc_id").add('required');
    } else {

        $("#vehicle_desc_id").removeAttr('required');
    }
}

我也尝试过其他方法:

document.getElementById("vehicle_desc_id").removeAttribute("requried");

document.getElementById("vehicle_desc_id ").required = true/false;

document.getElementById("vehicle_desc_id ").setAttribute("required ", "");

似乎没有任何效果...

None seems to be working...

推荐答案

当您对 html 进行排序并删除括号后的空格时有效，如果更正，则再次编辑以删除详细信息

works when you sort the html out and remove space after brackets, edited again to remove after details if corrected

function checkForRequired() {

    var plateLength = document.getElementById("plate_num_id").value.length;
var vehicle = document.getElementById("vehicle")
    if (plateLength < 1) {

        vehicle.setAttribute('required','required');
    } else {
 
      vehicle.removeAttribute('required');
    }
}

input:required{border:1px solid red;}

<input type="text" id="plate_num_id" name="plate_num" onblur/onfocusout="checkForRequired()"><br/><br>
<input type="text" id="vehicle" />

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