Liquid (Shopify Template Language) Interview Questions and Answers for 10 years experience

1. What is Liquid and how does it differ from other templating languages?

   • Answer: Liquid is a templating language created by Shopify. It's designed for e-commerce and focuses on security and ease of use. Unlike many other languages that might allow arbitrary code execution within templates, Liquid strictly separates logic from presentation, preventing potential vulnerabilities like cross-site scripting (XSS). It achieves this through its robust object model and a clear separation between variables, objects, tags, and filters. This makes it more secure and easier to maintain than languages with less stringent security features.

2. Explain the different object types in Liquid.

   • Answer: Liquid primarily works with objects. Key object types include: `Shopify objects` (e.g., `product`, `collection`, `customer`, `cart`), `arrays` (ordered lists), `hashes` (key-value pairs), and `strings` (text). Understanding these and how to access their properties and iterate through them is fundamental to Liquid development.

3. Describe the role of filters in Liquid and give examples.

   • Answer: Filters modify the output of objects. They are used to format data, manipulate strings, and perform other transformations. Examples include `date` (formats dates), `capitalize` (capitalizes the first letter), `truncate` (shortens strings), `money` (formats currency), `json` (converts data to JSON), and many more. They are applied using the pipe symbol (`|`).

4. How do you handle conditional logic in Liquid?

   • Answer: Liquid uses `if`, `elsif`, and `else` statements for conditional logic, enclosed within `{% %}` tags. These statements allow you to control which parts of the template are rendered based on the values of variables and objects. For example, `{% if product.available == true %}In Stock{% else %}Sold Out{% endif %}`.

5. Explain the use of loops in Liquid and provide examples.

   • Answer: Liquid uses `for` loops to iterate over arrays and objects. The syntax is `{% for item in array %}{{ item }}{% endfor %}`. You can also use `forloops` to access loop variables like `forloop.index`, `forloop.first`, `forloop.last`, etc., for conditional rendering within loops.

6. How do you include or reuse sections of code in Liquid templates?

   • Answer: You can use the `include` tag to insert reusable snippets of Liquid code from separate files. This promotes modularity and reusability. The `partial` tag in Shopify serves a similar purpose and can be preferred in certain contexts for better organization.

7. Describe the difference between `assign`, `capture`, and `increment` in Liquid.

   • Answer: `assign` creates or modifies a variable. `capture` stores the output of a block of Liquid code in a variable. `increment` increases the value of a numerical variable.

8. How do you handle errors in Liquid?

   • Answer: Liquid doesn't have explicit error handling mechanisms like `try...catch` blocks in other languages. Instead, you rely on careful variable checking and conditional statements to anticipate potential errors (e.g., checking for `null` values) and display fallback content or messages. Using filters thoughtfully can also help prevent errors.

9. Explain the importance of security in Liquid and how to prevent vulnerabilities.

   • Answer: Liquid's security model prevents arbitrary code execution, mitigating XSS and other attacks. However, careful coding practices are crucial. Sanitize any user-supplied input before using it in the template to prevent injection attacks. Avoid directly outputting untrusted data without appropriate filtering and escaping. Understand the capabilities and limitations of Liquid filters to ensure secure output.

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