{"id":4035,"date":"2012-04-30T06:30:37","date_gmt":"2012-04-30T12:30:37","guid":{"rendered":"http:\/\/www.vanseodesign.com\/?p=4035"},"modified":"2012-04-30T06:30:37","modified_gmt":"2012-04-30T12:30:37","slug":"block-element-modifier","status":"publish","type":"post","link":"https:\/\/vanseodesign.com\/css\/block-element-modifier\/","title":{"rendered":"BEM: The Block, Element, Modifier Approach To Decoupling HTML And CSS"},"content":{"rendered":"

For the last couple of months I’ve been talking a lot about giving our css best practices a refresh<\/a> and along the way have looked at approaches such as OOCSS, SMACSS, and DRY CSS. They all have some common underlying principles, one of which is the separation of structure and presentation.
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\nWe’ve all had this goal for years, but our practices haven’t really achieved it. Instead of decoupling our html and css we’ve been locking them ever tighter and making them more and more dependent on each other. I apologize if you’re getting tired of hearing me talk about coupling, but I think it’s a very important concept to understand if you want to develop scalable and maintainable websites<\/a>.<\/p>\n

Just last week Jonathan Snook, creator of SMACSS, brought up the very same topic<\/a> on Smashing Magazine. I want to touch on a few of the points he made and then give a quick walk through of yet another method (BEM) with similar goals to the ones we’ve been talking about.<\/p>\n

\"Rusty<\/a><\/p>\n

Decoupling HTML and CSS<\/h2>\n

Ideally we’d like to be able to completely rewrite our html or css without touching the other. That’s unlikely to happen all the time. There will often be a need to changes one after changing the other. However the less dependent our html and css are on each other, the better.<\/p>\n

Using OOCSS we reduce coupling by dropping descendent selectors<\/a> in favor of classes. With a DRY CSS approach we’re also using classes, but here the magic is based more on how we organize our css around stylistic groups. SMACSS falls somewhere in between these approaches.<\/p>\n

All agree we should move away from location based selectors as tying css selectors to a specific html structure leads to greater difficulty in changing either html or css. Inevitably we’re left managing specificity.<\/p>\n

Jonathan Snook refers to this as the depth of applicability<\/a> or in his words, “the depth at which a particular rule set impacts the elements around it.”<\/p>\n

For example consider the following code for a relatively simple navigation bar with a single drop down.<\/p>\n

{code type=html}<\/p>\n