Blogger is a very popular blogging platform that offers a lot of powerful features and tools to help bloggers better manage and publish their blog posts. One of these is the Blogger Expression Language (expr).


Blogger expression language is a template language based on JavaScript syntax, which allows bloggers to use data variables and conditional judgment functions to create dynamic templates. In Blogger, we can use the expression language to control the metadata of the blog, such as title, description, keywords, etc. These metadata are very important for search engine optimization (SEO) because they help search engines better understand your website content, which can improve your search rankings.


Below, I will introduce some commonly used Blogger expression languages, data variables and conditional judgment functions, and their usage in Blogger blogs.


1. Data variables

Blogger provides a lot of data variables, which can help us access various information of blogs, such as blog title, blog address, article title, article tags and so on. The following are some commonly used data variables:

  • data:blog.title - blog title
  • data:blog.url - Blog URL
  • data:blog.homepageUrl - blog home page address
  • data:blog.pageType - current page type (e.g. home page, article page, tag page, etc.)
  • data:blog.pageName - the name of the current page (e.g. post title, tag name, etc.)
  • data:blog.pageUrl - URL of the current page

We can use these variables in templates to dynamically generate blog metadata.

2. Condition judgment function

Blogger also provides many condition judgment functions, which can help us generate different content according to different conditions. The following are some commonly used conditional judgment functions:

  • b:if - executes the corresponding block of code if the condition is true
  • b:else - Executes the code block if the previous condition is not true
  • b:unless - execute the corresponding code block if the condition is not true
  • b:loop - Loop through a block of code, such as iterating over a list of tags or articles

Using these functions allows us to display different content in the template according to different conditions.

For example, we can judge whether the current page is the homepage in the template, if it is the homepage, then display a welcome sentence, otherwise display a brief introduction. code show as below:

<b:if cond='data:blog.url == data:blog.homepageUrl'>
   <p>Welcome to my blog! </p>
<b:else/>
   <p>This is a technical blog sharing knowledge about programming and computer science. </p>
</b:if>

In the above code, we use two data variables data:blog.url and data:blog.homepageUrl to determine whether the current page is the home page. If so, display a welcome statement; otherwise, display a brief introduction.

How to use data variables combined with conditional judgment:

<b:if cond='data:blog.pageType == &quot;item&quot;'> 
  <h2><data:post.title/></h2> 
  <p><data:post.dateHeader/></p> 
<b:else/> 
  <h2><data:blog.title/></h2> 
  <p><data:blog.description/></p> 
</b:if>

In the above code, the data variable data:blog.pageType is used to determine whether the current page type is an article page. If it is an article page, display the article title and publication date; otherwise, display the blog title and description. The conditional judgment function b:if and the conditional expression data:blog.pageType == &quot;item&quot; are used here.

in conclusion
In this article, we introduce the expression language (expr) of Blogger templates and commonly used data variables and conditional judgment functions. By using these functions, we can customize our blog template more flexibly to make it more suitable for our needs.

Of course, what is introduced here is just the basic knowledge of Blogger templates. If you want to learn more about Blogger template development, you need to learn more knowledge, such as custom functions, loop statements, etc. I hope this article is helpful to you, and I wish you go further and further on the road of blogging!

Author： yuday Posts：About the use of data variables and conditional judgment in Blogger