Javascript Course


createElement() and insertBefore() are two JavaScript methods used to add new HTML elements in the web page, these elements are created dynamically in memory and added by JavaScript.


createElement()

createElement(tagName) creates in memory an HTML element of the tag specified by tagName.

Syntax:
var new_tag = document.createElement(tagName);
- tagName is the name of the tag that will be created.
- new_tag is the variable that stores the object of the created element.

For example, the code below creates a <div> tag, and adds to it a class attribute and content.
var elm = document.createElement('div');
elm.setAttribute('class', 'o_clasa')
elm.innerHTML ='Text in div tag';
console.log(elm);
- This code will create in memory an object that contains the fallowing HTML code:
<div class='o_clasa'>Text in div tag</div></div>

- To add this element in the HTML document structure, you can use the appendChild() method.
In this example, the 'div' element stored in 'elm' is added as the last child in HTML body.
var elm = document.createElement('div');
elm.setAttribute('class', 'o_clasa')
elm.innerHTML ='Div created with createElement(), and added with appendChild()';
document.body.appendChild(elm);

insertBefore()

insertBefore() adds a child node in front of another child, both inside a parent element.
Syntax:
parent.insertBefore(newElm, reference);
- Inserts newElm before reference inside the parent.

Example, creates a <h3> tag and adds it before a <div> with id='rpr':
<h4>Example with insertBefore()</h4>
<p>If you click the button, it adds a H3 tag created with createElement(), before a DIV with id='rpr'.</p>
<button id='btn1'>Add H3</button>
<div id='rpr'>#rpr, reper.</div>

<script>
function add_h3(){
 // creates a H3 element, class and html content
 var elm = document.createElement('h3');
 elm.className ='o_clasa';
 elm.innerHTML = 'The <b>html text</b> content';

 //gets the reference tag
 var reper = document.getElementById('rpr');

 //adds the new element before reper (in parent body)
 document.body.insertBefore(elm, reper);
}

document.getElementById('btn1').addEventListener('click', add_h3);
</script>

Adding dynamically input fields in Form

Here is a practical and useful example of using createElement() and insertBefore() methods to automatically add text fields in a form.
Explanations are in the script code.
<h4>Example adding with insertBefore() input fields in form</h4>
<p>When you click on the 'Add Box' button, the add_input() function creates and adds a text field in form.</p>

<form action='#'>
 <input type='text' name='nume[]' />
 <input type='submit' value='Submit' id='submit' /><br><br>
 <input type='button' value='Add box' onclick='add_input()' />
</form>

<script>
// creates an input element and adds it before the Submit button
function add_input() {
 // sets a new input element, having the attributes: type=text si name=nume[]
 var elm = document.createElement('input');
 elm.setAttribute('type', 'text');
 elm.setAttribute('name', 'nume[]');
 elm.style.display = 'block'; // sets css style display:block;

 // sets the objects for reference and parent
 var reper = document.getElementById('submit');
 var parinte = reper.parentNode;

 // Adds elm
 parinte.insertBefore(elm, reper);
}
</script>

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
What attribute makes the input text box to not be modified by the user?
checked="checked" readonly="readonly" disabled="disabled"
<input type="text" value="fixed-value" readonly="readonly" name="a_name" />
What CSS property allows you to create rounded corners in your webpage design?
background-size border-size border-radius
.class {
  border:2px solid blue;
  border-radius:1.2em;
}
What instruction displays a confirmation dialog box to the viewer, who must then click OK or Cancel to proceed?
indexOf() confirm() prompt()
var ques = window.confirm("The result of 0+0 is 0?");
if (ques) alert("Corect");
else alert("Incorrect");
Indicate the PHP function that returns the lowest number of the parameter values.
floor() ceil() min()
$min_nr = min(12, 8, 25, 13);
echo $min_nr;        // 8
createElement and insertBefore

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