Javascript Course

In this page it is presented a JavaScript function that can be used to get the values of the selected (checked) checkboxes added into a form. The function receives the object with that form, then, returns an Array with the value of each selected /checked checkbox into that <form>

Code of the function

// Returns an array with values of the selected (checked) checkboxes in 'frm'
function getSelectedChbox(frm){
 // JavaScript & jQuery Course - https://coursesweb.net/javascript
 var selchbox =[]; // array that will store the value of selected checkboxes

 // gets all the input tags in frm, and their number
 var inpfields = frm.getElementsByTagName('input');

 // traverse the inpfields elements, and adds the value of selected (checked) checkbox in selchbox
 for(var i=0; i<inpfields.length; i++) {
 if(inpfields[i].type =='checkbox' && inpfields[i].checked == true) selchbox.push(inpfields[i].value);
 }

 return selchbox;
}

Example usage getSelectedChbox() function. When click on a button into a form with various checkboxes, it opens an alert window with the values of the selected checkboxes.
<h4>Example getting value of the selected checkboxes</h4>
<p>Select some checkboxes, then click the Click button.</p>

Check the web site programming language you know:
<form action='script.php' method='post'>
<input type='checkbox' name='chb[]' value='html' />HTML<br>
<input type='checkbox' name='chb[]' value='css' />CSS<br>
<input type='checkbox' name='chb[]' value='javascript' />JavaScript<br>
<input type='checkbox' name='chb[]' value='php' />php<br>
<input type='checkbox' name='chb[]' value='python' />Python<br>
<input type='checkbox' name='chb[]' value='net' />Net<br>
<input type='button' value='Click' id='btntest' />
</form>

<script>
// Returns an array with values of the selected (checked) checkboxes in 'frm'
function getSelectedChbox(frm){
 // JavaScript & jQuery Course - https://coursesweb.net/javascript
 var selchbox = []; // array that will store the value of selected checkboxes

 // gets all the input tags in frm, and their number
 var inpfields = frm.getElementsByTagName('input');

 // traverse the inpfields elements, and adds the value of selected (checked) checkbox in selchbox
 for(var i=0; i<inpfields.length; i++){
 if(inpfields[i].type =='checkbox' && inpfields[i].checked == true) selchbox.push(inpfields[i].value);
 }

 return selchbox;
}

 /* Test this function */
// When click on #btntest, alert the selected values
document.getElementById('btntest').onclick = function(){
 var selchb = getSelectedChbox(this.form); // gets the array returned by getSelectedChbox()
 alert(selchb);
}
</script>

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which attribute is used in <a> tag for the address of the link?
src href rel
<a href="http://coursesweb.net/" title="CoursesWeb.net">CoursesWeb.net</a>
Which CSS property sets the type of the text font?
font-family text-decoration font-size
h2 {
  font-family:"Calibri",sans-serif;
}
What instruction selects all the <div> tags with class="cls"?
querySelector("div.cls") getElementsByTagName("div") querySelectorAll("div.cls")
var elm_list = document.querySelectorAll("div.cls");
var nr_elms = elm_list.length;       // number of selected items
alert(nr_elms);
Indicate the function that can be used to get the sum of values in an array.
array_sum() array_diff() array_shift()
$arr =[1, 2, 3, 4);
$arr_sum = array_sum($arr);
echo $arr_sum;       // 10
Get the value of the selected /checked checkboxes in a form

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