An id on an <input> tag assigns an identifier to the input control.
The identifier must be unique across the page.
A unique id attribute on each of the 4 <input> elements.
<form action="/tutorial/action.html">
<fieldset>
<legend>Contact Details</legend>
<input type="text" placeholder="First name" id="firstname" name="firstname"><br /><br />
<input type="text" placeholder="Last name" id="lastname" name="lastname"><br /><br />
<input type="text" placeholder="Email" id="email" name="email"><br /><br />
<input type="submit" id="submit" value="Submit">
</fieldset>
</form>
The id attribute assigns an identifier to the <input> element.
The id allows JavaScript to easily access the <input> element.
It is also used to point to a specific id selector in a style sheet.
Tip: id is a global attribute that can be applied to any HTML element.
<input id="identifier" />
| Value | Description |
|---|---|
| identifier | A unique alphanumeric string. The id value must begin with a letter ([aside-Zaside-z]) and may be followed by any number of letters, digits ([0-9]), hyphens (-), underscores (_), colons (:), and periods (.). |
An <input> element with a unique id.
Clicking the button will display the <value> of the input field.
<label>Title</label><br />
<input id="myinput" type="text" value="Computer Literacy">
<br/><br/>
<button onclick="show();">Show input value</button>
<script>
let show = () => {
let input = document.getElementById("myinput");
alert("Value = " + input.value);
}
</script>
The id attribute assigns a unique identifier for the <input> element.
Clicking the button calls JavaScript which locates the <input> using the id.
Finally, the value of the <input> element is displayed in an alert box.
Here is when id support started for each browser:
 Chrome
|
1.0 | Sep 2008 |
 Firefox
|
1.0 | Sep 2002 |
 IE/Edge
|
1.0 | Aug 1995 |
 Opera
|
1.0 | Jan 2006 |
 Safari
|
1.0 | Jan 2003 |
