Everyone who is familiar with CSS !important statement understood that it means that the style have the highest priority regardless of other priority. However, !important should be avoided as much as possible and order priority should be practice in CSS instead. In jQuery, there are times when we need to change the styling of our web program but programmers usually lack of such knowledge and inquire whether !important is available for jQuery css() method. In this article, we will discuss jQuery css() and JavaScript methods in term of using !important definition.
jQuery CSS !important
One thing that everyone must have wonder (those that haven't tried yet) is whether jQuery support declaration of !important for their css() method such as this.
1 | jQuery('#id').css('height', '200px !important'); |
You will find that nothing will happen with a declaration of such manipulation. If we were to try out on pure JavaScript with the above declaration, it will be something like this.
1 | document.getElementById('id').style.height = "200px !important"; |
Having a pure JavaScript instruction such as this will not work in most browser other than safari 3++. Hence, jQuery will definitely won't work too. This is not a bug but something that most browser doesn't acknowledge a need since inline style already have the highest priority other than user defined ones. (unless you do not want your user to change how they view your website).
Solution to jQuery CSS !important
Well, the typical way of getting !important will not work. Rather, you might want to try CSS DOM cssText. Hence, you will force !important to your jQuery statement by doing this.
1 | jQuery('#id').css('cssText', 'height: 200px !important'); |
However, most people will be unfamiliar with cssText. cssText will overwrites the css of that particular element. Hence, you will have to redeclare the rule for that particular element all over again. On the other hand, if you are using JavaScript cssText, different browser treat cssText different such as ie you will define this way,
1 | document.getElementById('id').style.cssText = 'height: 200px !important' |
While normally you will use it this way.
1 | document.getElementById('id').cssText = 'height: 200px !important' |
Definitely, there is a better alternative such as using the cssRules/rules array which can specify the rule in that element to be modify.
The other more practical way of doing it is by introducing new class for your element. Instead of styling through jQuery or DOM object which is applying inline styling (means highest priority already), you should leave every majority styling or best all of the styling to an external style sheet that help you reduce some bytes on the script and also improve maintainability for both your code and style. You can do this using the toggleClass which adds a new class to that element automatically.
1 | jQuery('#id').toggleClass('classname'); |
or you can do this in JavaScript by replacing the class (this is more efficient than the jQuery one since there isn't any additional checking and stuff)
1 | document.getElementById('id').className = 'classname'; |
Summary
Using !important in CSS is not advisable since it might kill your web usability. Furthermore, there is no reason why !important should be use as inline styling already has the highest priority. Hence, you might want to reconsider applying !important on your script after thinking about the consequences that might bought to your users.
来自 http://hungred.com/how-to/jquery-javascript-css-important/