How to select all in javascript

With the development of web applications, more and more web applications need to provide the select all function, so that users can select or cancel many options on the page at the same time. In Javascript, it is very simple to implement the select all function. This article will introduce how to use Javascript to implement the select all function.

First, we need to add a select all checkbox to the HTML page. This checkbox needs to have a specific identifier, in our case we use "selectAll" as the identifier. This checkbox should be placed on top of other checkboxes to make its purpose clear to the user.

<input type="checkbox" id="selectAll"> 全选

Then, in Javascript, we need to select all other checkboxes and keep their checked state consistent with the Select All checkbox. This can be easily done using the $() function in Javascript frameworks. The code to select all other checkboxes is as follows:

var checkboxes = document.querySelectorAll('input[type=checkbox]:not(#selectAll)');

Next, we can use the forEach() function to iterate through all the checkboxes and change their selected status when the all-selected checkbox status changes. Adjustment. See the code below:

var selectAll = document.getElementById('selectAll');
var checkboxes = document.querySelectorAll('input[type=checkbox]:not(#selectAll)');

selectAll.addEventListener('change', function () {
    checkboxes.forEach(function (checkbox) {
        checkbox.checked = selectAll.checked;
    });
});

Finally, we need to make sure that the status of every other checkbox is also monitored so that the status of the select all checkbox is updated if necessary. We can easily do this using the following code snippet:

checkboxes.forEach(function (checkbox) {
    checkbox.addEventListener('change', function () {
        var allChecked = true;
        for (var i = 0; i < checkboxes.length; i++) {
            if (!checkboxes[i].checked) {
                allChecked = false;
                break;
            }
        }
        selectAll.checked = allChecked;
    });
});

This will handle the state changes of both the selected all checkbox and other checkboxes to ensure that the options are always up to date.

So far, we have successfully implemented the select all function. The complete code is as follows:

<input type="checkbox" id="selectAll"> 全选

 选项 1
 选项 2
 选项 3
 选项 4

<script>
    var selectAll = document.getElementById('selectAll');
    var checkboxes = document.querySelectorAll('input[type=checkbox]:not(#selectAll)');

    selectAll.addEventListener('change', function () {
        checkboxes.forEach(function (checkbox) {
            checkbox.checked = selectAll.checked;
        });
    });

    checkboxes.forEach(function (checkbox) {
        checkbox.addEventListener('change', function () {
            var allChecked = true;
            for (var i = 0; i < checkboxes.length; i++) {
                if (!checkboxes[i].checked) {
                    allChecked = false;
                    break;
                }
            }
            selectAll.checked = allChecked;
        });
    });
</script>

In actual applications, it can be customized according to specific needs. For example, you can change the styles of other elements when all are selected, or include other form elements such as links and text boxes in the options. In any case, Javascript provides a simple yet functional solution that can help us implement various select-all functions easily.

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