When designing or editing a Blogger theme, you often need to set a default value if certain data is missing. This is where the Elvis operator (?:) comes in handy. It allows you to simplify your code, improve template performance, and keep everything clean without writing long if-else conditions.
Table of Contents
- What is the Elvis Operator?
- Where Does It Come From?
- Syntax Types
- Practical Examples in Blogger
- Common Mistakes and Troubleshooting
- Pro Tips for Advanced Users
- FAQ – Frequently Asked Questions
- Final Thoughts
What is the Elvis Operator?
The coalescence (Elvis) operator is a Blogger XML expression that lets you select the first available (non-empty) value from a list. This is extremely useful in themes where some values may not exist for every post, page, or gadget.
data:view.featuredImage ?: "https://example.com/default.jpg"In this example, Blogger will use data:view.featuredImage if available; otherwise, it falls back to the default image.
Where Does It Come From?
The Elvis operator concept first appeared in C# (2003) as the null-coalescing operator (??). Later, languages like Kotlin and Groovy adopted the syntax ?:, which visually resembles Elvis Presley’s famous hairstyle—hence the name. Blogger integrated this operator in its 2015 template language update.
Syntax Types
1. Infix Syntax (Most Common)
value1 ?: value2Best for two-value scenarios.
2. Functional Syntax (For Multiple Fallbacks)
?:(value1, value2, value3, value4)Recommended when you have three or more possible values.
Practical Examples in Blogger
1. Fallback Featured Image
<img expr:src='data:view.featuredImage ?: "https://your-blog.com/fallback.jpg"' />This ensures your post always has an image, even if the featured image is missing.
2. Multi-ID Selector
<b:with value='?:(data:customId, data:view.postId, data:view.pageId, data:blog.blogId)' var='itemId'>
<b:eval expr='data:itemId'/>
</b:with>3. Link Unification for Different Gadgets
<b:loop values='?:(data:links, data:labels)' var='link'>
<a expr:href='?:(data:link.href, data:link.url)'>
<b:eval expr='?:(data:link.title, data:link.name)'/>
</a>
</b:loop>4. Fallback Meta Description
<meta expr:content='data:blog.metaDescription ?: "Welcome to my Blogger site!"' name="description"/>5. Default Author Name
<span>Author: <b:eval expr='data:post.author.name ?: "Unknown Author"'/></span>Common Mistakes and Troubleshooting
- Empty string fallback issue: Sometimes Blogger treats empty fields as valid. Use conditions like
!= ""to avoid blank outputs. - Overusing nested operators: Too many
?:in a row makes your code hard to read. Use<b:with>instead. - Wrong value order: Always put the most likely value first; Blogger evaluates from left to right.
Pro Tips for Advanced Users
- Use this operator to set SEO-friendly meta tags dynamically.
- Combine it with conditional expressions for more flexibility.
- When designing templates, keep a global fallback image & author for better branding.
- Minimize manual checks with
?:for a cleaner, faster-loading Blogger theme.
FAQ – Frequently Asked Questions
1. Does the Elvis operator improve Blogger SEO?
Indirectly, yes. Cleaner code improves load time and consistency, which are factors search engines consider.
2. Can I use it for text, images, links, and numbers?
Yes, it works with any valid Blogger data type.
3. Is it supported in all Blogger themes?
Yes, all modern Blogger templates support it since 2015.
4. Does it work with empty arrays?
No, empty arrays are considered empty, and the fallback will be used.
5. Will it break my template if I use it incorrectly?
No, but it may return a blank value if improperly configured.
6. Can I chain more than three values?
Yes, the functional syntax allows multiple fallbacks.
Final Thoughts
The Elvis operator is a powerful but underrated feature in Blogger. It simplifies your code, saves time, and helps your blog display consistent information across posts, pages, and gadgets. Whether you’re building a custom Blogger template or just tweaking your existing one, mastering this operator is a small step that can make a big difference.