2) Custom Attributes in Html and How to Read Them?
In this article, I am going to show you lot how yous can use HTML5 custom data attributes. I'm also going to present yous with some employ cases that you can find helpful in your work as a developer.
Why Custom Data Attributes?
Very often we need to shop information associated with dissimilar DOM elements. This information might not exist essential for readers, but having easy access to it would brand life a lot easier for usa developers.
For instance, let'south say you lot have a list of dissimilar restaurants on a webpage. Earlier HTML5, if you wanted to store information about the blazon of food offered by restaurants or their distance from the visitor, you would accept used the HTML class attribute. What if you lot too needed to store the restaurant id to see which particular eating house the user would desire to visit?
Here are a few issues with the approach based on the HTML class attribute.
- The HTML class attribute is non meant to store information similar this. Its main purpose is to allow the developer to assign fashion information to a set of elements.
- Each additional piece of information requires united states to add a new class to our element. This makes it harder to parse the data in JavaScript to actually get what we need.
- Allow's say a given class proper name begins with numbers. If you make up one's mind to afterward way the elements based on that data in the class proper noun, yous will have to either escape the number or use attribute selectors in your stylesheet.
To go rid of these problems, HTML5 has introduced custom data attributes. All attributes on an element whose proper name starts with data- are data attributes. You can also employ these information attributes to style your elements.
Next, let's dive into the basics of data attributes and learn how to access their values in CSS and JavaScript.
The HTML Syntax
Every bit I mentioned earlier, the name of a data attribute will e'er showtime with data-. Here is an instance:
<li information-type = "veg" data-distance = "2miles" data-identifier = "10318" > Salad Male monarch </li > You lot tin can now use these information attributes to search and sort restaurants for your visitors. For case, you can now show them all the vegetarian restaurants inside a certain distance.
Besides the information- prefix, the name of a valid custom information attribute must contain only letters, numbers, hyphen (-), dot (.), colon (:) or underscore (_). It cannot contain majuscule letters.
In that location are two things that you should keep in heed when using data attributes.
Starting time, information stored in these attributes should be of blazon string. Anything that tin be string-encoded can exist stored in information attributes as well. All the type conversions volition demand to be done in JavaScript.
Second, data attributes should only exist used when there are no other appropriate HTML elements or attributes. For example, information technology is not appropriate to store an chemical element'due south class in information-class attribute.
An element can accept whatsoever number of data attributes with any value you want.
Data Attributes and CSS
You can utilise data attributes in CSS to style elements using aspect selectors. You can also show the data stored in the data attribute to users (in a tooltip or some other way) with the help of the attr() function.
Styling Elements
Getting back to our eating place example, y'all tin can give users a cue about the type of restaurant or its altitude from them using attribute selectors to mode the background of the restaurants differently. Hither is an instance:
li [ data-type = 'veg' ] { groundwork : #8BC34A ; } li [ data-type = 'french' ] { groundwork : #3F51B5 ; } Run into the Pen Styling elements with data attributes past SitePoint (@SitePoint) on CodePen.
Creating Tooltips
You lot tin apply tooltips to show users some additional information related to an chemical element.
I recommend you employ this method for quick prototypes rather than a production website, not to the lowest degree because CSS-only tooltips are not fully accessible.
The information that you lot want to testify can be stored in a data-tooltip attribute.
<span data-tooltip = "A simple caption" > Give-and-take </span > Yous tin then present the data to the user with the ::before pseudo element.
bridge::earlier { content : attr (data-tooltip) ; // More Mode Rules } span:hover ::before { display : inline-block; } See the Pen Creating tooltips with information attributes past SitePoint (@SitePoint) on CodePen.
Accessing Information Attributes with JavaScript
In that location are three means of accessing data attributes in JavaScript.
Using getAttribute and setAttribute
You can utilise getAttribute() and setAttribute() in JavaScript to go and fix the value of different data attributes.
The getAttribute method will either return null or an empty string if the given attribute does non exist. Hither is an instance of using these methods:
var restaurant = certificate . getElementById ( "restaurantId" ) ; var ratings = restaurant. getAttribute ( "data-ratings" ) ; You can use the setAttribute method to change the value of existing attributes or to add new attributes.
restaurant. setAttribute ( "data-owner-proper noun" , "someName" ) ; Using the dataset Property
A simpler method of accessing data attributes is with the help of the dataset property. This holding returns a DOMStringMap object with one entry for each custom information attribute.
There are a few things that you should go along in listen while using the dataset property.
It takes three steps to transform a custom information attribute into a DOMStringMap key:
- The
data-prefix is removed from the attribute name - Any hyphen followed past a lower case alphabetic character is removed from the name and the letter post-obit it is converted to uppercase
- Other characters will remain unchanged. This means that any hyphen that is not followed by a lowercase letter of the alphabet will also remain unchanged.
The attributes can then be accessed using the camelCase name stored in the object as a cardinal like chemical element.dataset.keyname.
Another style of accessing the attributes is using bracket notation, like element.dataset[keyname]
Consider the following HTML:
<li data-blazon = "veg" information-distance = "2miles" data-identifier = "10318" data-owner-proper noun = "someName" > Salad King </li > Here are a few examples:
var restaurant = document . getElementById ( "restaurantId" ) ; var ratings = restaurant. dataset . ratings ; eating house. dataset . ratings = newRating; var possessor = eating house. dataset [ 'ownerName' ] ; restaurant. dataset [ 'ownerName' ] = 'newOwner' ; This method is at present supported in all major browsers and you should favor it over the previous method for accessing custom information attributes.
Using jQuery
You can also use the jQuery data() method to admission data attributes of an chemical element. Earlier jQuery version 1.six, you had to use the following code to access data attributes:
var eating house = $ ( "#restaurantId" ) ; var owner = restaurant. data ( "owner-name" ) ; eating house. data ( "possessor-proper name" , "newName" ) ; From version 1.6, jQuery started using the camelCase version of information attributes. Now, yous can do the same thing using the following code:
var restaurant = $ ( "#restaurantId" ) ; var owner = restaurant. data ( "ownerName" ) ; restaurant. data ( "ownerName" , "newName" ) ; You lot should know that jQuery also tries to internally convert the string obtained from a data aspect into a suitable type like numbers, booleans, objects, arrays and zero.
var eating house = $ ( "#restaurantId" ) ; var identifier = restaurant. data ( "identifier" ) ; console . log ( typeof identifier) ; // number If you want jQuery to get the value of an aspect every bit a string without whatsoever attempt to convert it into other types, you should use jQuery'southward attr() method.
jQuery only retrieves the value of data attributes the kickoff time they are accessed. The data attributes are then no longer accessed or changed. All the changes that you brand to those attributes are made internally and accessible only within jQuery.
Let'southward presume you lot are manipulating the information attributes of the following list particular:
<li id = "salad" data-type = "veg" data-distance = "2miles" data-identifier = "10318" > Salad Rex </li > You can use the code below to modify the value of its data-altitude attribute:
var distance = $ ( "#salad" ) . data ( "distance" ) ; panel . log (distance) ; // "2miles" $ ( "#salad" ) . information ( "distance" , "1.5miles" ) ; console . log (distance) ; // "one.5miles" document . getElementById ( "salad" ) . dataset . distance ; // "2miles" As you lot can see, accessing the value of the information-distance aspect using vanilla JavaScript (not jQuery) keeps giving us the onetime result.
Conclusion
In this tutorial I accept covered all the important things that you need to know most HTML5 information attributes. Besides creating tooltips and styling elements using attribute selectors, you can utilise information attributes to store and show users some other information like a notification about unread messages and so on.
If y'all have any other questions about information attributes, let me know in the comments.
Source: https://www.sitepoint.com/how-why-use-html5-custom-data-attributes/
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