Check whether input checkbox is empty using JavaScript-CodePudding

I currently have a filter dropdown containing checkboxes. I have checkboxes for gender and category. I am now trying to make sure that the user will check at least one checkbox each part (gender and category). The problem is I don't know how to check whether the checkbox is empty or not.

Below is the partial form for the filter dropdown:

<form  method="GET" action="manage_product.php">
    <h6 >Gender</h6>
    <div >
        <input  name="genderFil[]" type="checkbox" value="M"  id="genMale" <?= ($isMale == 1) ? "checked" : ""; ?>>
        <label  for="genMale">Male</label>
    </div>
    <div >
        <input  name="genderFil[]" type="checkbox" value="F"  id="genFemale" <?= ($isFemale == 1) ? "checked" : ""; ?>>
        <label  for="genFemale">Female</label>
    </div>

    <div ></div>

    <h6 >Category</h6>
    <div >
        <input  name="categoryFil[]" type="checkbox" value="1"  id="catShoes" <?= ($isShoes == 1) ? "checked" : ""; ?>>
        <label  for="catShoes">Shoes</label>
    </div>
    <div >
        <input  name="categoryFil[]" type="checkbox" value="2"  id="catPants" <?= ($isPants == 1) ? "checked" : ""; ?>>
        <label  for="catPants">Pants</label>
    </div>
    <div >
        <input  name="categoryFil[]" type="checkbox" value="3"  id="catShirts" <?= ($isShirts == 1) ? "checked" : ""; ?>>
        <label  for="catShirts">Shirts</label>
    </div>

    <div ></div>
    <input type="submit"  name="applyFilter" value="Apply" onclick="checkFilter()">
</form>

Below is the javascript that I tried to code:

        function checkFilter()
        {
            var res = true;

            var checkedGender = $('input[]:checked').length;
            if(checkedGender < 1)
            {
                alert("Please select at least one gender!");
                res = false;
            }

            var checkedCategory = $('input[]:checked').length;
            if(checkedCategory < 1)
            {
                alert("Please select at least one category!");
                res = false;
            }
            
            return res;
        }

It is only can be submitted if there is at least one gender and at least one category checked.

How can I check whether the checkbox is empty or not?

CodePudding user response：

A checkbox has two states: checked and unchecked.

To get the state of a checkbox, you follow these steps:

First, select the checkbox using a DOM method such as getElementById() or querySelector(). Then, access the checked property of the checkbox element. If its checked property is true, then the checkbox is checked; otherwise, it is not.

CodePudding user response：

To check whether a checkbox is empty or not using JavaScript, you can use the querySelectorAll() method to select all the checkbox elements in the form, and then check the length property of the resulting NodeList to see if it is greater than 0.

Here's an example of how you can use this approach to check whether the checkbox is empty or not:

// Get the form element
const form = document.querySelector("form");

// Get all the checkbox elements in the form
const checkboxes = form.querySelectorAll('input[type="checkbox"]');

// Check if there are any checkboxes in the form
if (checkboxes.length === 0) {
  // There are no checkboxes in the form, so the checkbox is empty
  console.log("The checkbox is empty");
} else {
  // There are checkboxes in the form, so the checkbox is not empty
  console.log("The checkbox is not empty");
}

In your specific case, you can use the querySelectorAll() method to select all the checkboxes with the genderFil and categoryFil classes, and then check the length property of the resulting NodeLists to see if there are any checked checkboxes in each group. If there are no checked checkboxes in either group, you can show an alert message to the user and prevent the form from being submitted.

Here's how you can modify your checkFilter() function to use this approach:

function checkFilter() {
  // Select all the checkboxes with the "genderFil" class
  const genderCheckboxes = document.querySelectorAll('.genderFil');

  // Check if there are any checked checkboxes in the "genderFil" group
  if (genderCheckboxes.length === 0) {
    // There are no checked checkboxes in the "genderFil" group
    alert("Please select at least one gender!");
    return false;
  }

  // Select all the checkboxes with the "categoryFil" class
  const categoryCheckboxes = document.querySelectorAll('.categoryFil');

  // Check if there are any checked checkboxes in the "categoryFil" group
  if (categoryCheckboxes.length === 0) {
    // There are no checked checkboxes in the "categoryFil" group
    alert("Please select at least one category!");
    return false;
  }

  // If there are checked checkboxes in both groups, allow the form to be submitted
  return true;
}

CodePudding user response：

This will work.

function checkFilter()
{
    var res = true;


    var checkedGender = document.getElementById('genderSelector').querySelectorAll('input[type="checkbox"]:checked').length;        
    if(checkedGender < 1)
    {
        alert("Please select at least one gender!");
        res = false;
        return  res;
    }


    var checkedCategory = document.getElementById('categorySelector').querySelectorAll('input[type="checkbox"]:checked').length;
    if(checkedCategory < 1)
    {
        alert("Please select at least one category!");
        res = false;
        return res;
    }

    return res;
}

<form  method="GET" action="manage_product.php" onsubmit="return checkFilter();">
    <div id="genderSelector">
        <h6 >Gender</h6>
        <div >
            <input  name="genderFil[]" type="checkbox" value="M"  id="genMale" <?= ($isMale == 1) ? "checked" : ""; ?>>
            <label  for="genMale">Male</label>
        </div>
        <div >
            <input  name="genderFil[]" type="checkbox" value="F"  id="genFemale" <?= ($isFemale == 1) ? "checked" : ""; ?>>
            <label  for="genFemale">Female</label>
        </div>
    </div>

    <div ></div>

    <div id="categorySelector">
        <h6 >Category</h6>
        <div >
            <input  name="categoryFil[]" type="checkbox" value="1"  id="catShoes" <?= ($isShoes == 1) ? "checked" : ""; ?>>
            <label  for="catShoes">Shoes</label>
        </div>
        <div >
            <input  name="categoryFil[]" type="checkbox" value="2"  id="catPants" <?= ($isPants == 1) ? "checked" : ""; ?>>
            <label  for="catPants">Pants</label>
        </div>
        <div >
            <input  name="categoryFil[]" type="checkbox" value="3"  id="catShirts" <?= ($isShirts == 1) ? "checked" : ""; ?>>
            <label  for="catShirts">Shirts</label>
        </div>
    </div>

    <div ></div>
    <input type="submit"  name="applyFilter" value="Apply">
</form>