This content originally appeared on Go Make Things and was authored by Go Make Things
Today, we’re going to look at how to get, set, and remove attributes and properties with vanilla JS. We’ll also learn the difference between attributes and properties, and some “gotchas” when working with them.
Let’s dig in!
The Element.*Attribute() methods
You can use the Element.getAttribute(), Element.setAttribute(), Element.removeAttribute(), and Element.hasAttribute() methods to get, set, remove, and check for the existence of attributes (including data attributes) on an element, respectively.
If an attribute does not exist on an element, the Element.getAttribute() method returns null.
let elem = document.querySelector('#lunch');
// Get the value of the [data-sandwich] attribute
let sandwich = elem.getAttribute('data-sandwich');
// Set a value for the [data-sandwich] attribute
elem.setAttribute('data-sandwich', 'turkey');
// Remove the [data-chips] attribute
elem.removeAttribute('data-chips');
// Check if an element has the `[data-drink]` attribute
if (elem.hasAttribute('data-drink')) {
console.log('Add a drink!');
}
Element properties
HTML elements have dozens of properties that you can access directly.
Some of them are read only, meaning you can get their value but not set it. Others can be used to both read and set values. You can find a full list on the Mozilla Developer Network.
let elem = document.querySelector('#main');
// Get the ID of the element
// returns "main"
let id = elem.id;
// Set the ID of the element
elem.id = 'secondary';
// Get the parentNode of the element
// This property is read-only
let parent = elem.parentNode;
What’s the difference between attributes and properties?
In JavaScript, an element has attributes and properties. The terms are often used interchangeably, but they’re actually two separate things.
An attribute is the initial state when rendered in the DOM. A property is the current state.
In most cases, attributes and properties are kept in-sync automatically. For example, when you use Element.setAttribute() to update an ID attribute, the id property is updated as well.
<p>Hello</p>let p = document.querySelector('p');
// Update the ID
p.setAttribute('id', 'first-paragraph');
// These both return "first-paragraph"
let id1 = p.getAttribute('id');
let id2 = p.id;
However, user-changeable form properties—noteably, value, checked, and selected—are not automatically synced.
<label for="greeting">Greeting</label>
<input type="text" id="greeting">let greeting = document.querySelector('#greeting');
// Update the value
greeting.setAttribute('value', 'Hello there!');
// If you haven't made any updates to the field, these both return "Hello there!"
// If you HAVE updated the field, val1 returns whatever was typed in the field instead
let val1 = greeting.value;
let val2 = greeting.getAttribute('value');
If you try to update the value property directly, that will update the UI.
greeting.value = 'Hello there!';
This allows you to choose different approaches depending on whether you want to overwrite user updates or not.
If you want to update a field, but only if the user hasn’t made any changes, use Element.setAttribute(). If you want to overwrite anything they’ve done, use the value property.
This content originally appeared on Go Make Things and was authored by Go Make Things
Go Make Things | Sciencx (2022-01-19T15:30:00+00:00) How to get, set, and remove attributes and properties with vanilla JavaScript. Retrieved from https://www.scien.cx/2022/01/19/how-to-get-set-and-remove-attributes-and-properties-with-vanilla-javascript/
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