Скачать или смотреть Mastering XPath: Extracting Text Not Inside a Tag

Learn how to effectively use XPath to retrieve text nodes outside of tags. This guide explains the nuances of accessing text not enclosed in tags and offers practical XPath solutions.
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Extracting Text Not Inside a Tag Using XPath

XPath is a powerful language used for navigating and querying XML and HTML documents. However, sometimes it can present challenges, especially when trying to extract text that resides outside of tags. In this post, we'll explore a common problem beginners face with XPath: retrieving text that is not encapsulated within tags, specifically the case of extracting the number 2 from the following HTML structure:

[[See Video to Reveal this Text or Code Snippet]]

The primary challenge here lies in the fact that the number 2 is not inside any tag, which complicates the extraction process. Let's break down the solution step by step.

The Problem

You have an HTML or XML snippet where you want to retrieve a text node that is outside of any tags. For instance, in the example above, the desired output is 2, which comes immediately after the <em> tag. The issue arises when trying to access 2 using simple queries, particularly with spaces involved. Attempting to use /p/text() fails if there's a space between <p> and <em>; thus, you need a more sophisticated approach.

The Solution

To obtain the text node that contains 2, you can use the following XPath expressions:

1. Selecting the Following Sibling Text Node

The following XPath expression will successfully select the text node that contains your target value:

[[See Video to Reveal this Text or Code Snippet]]

This query works well because it navigates to the <em> child first and then looks for a sibling text node that follows it. The important note here is that this XPath will include any spaces in the text node, so it might return " 2" (with leading space).

2. Normalizing Space for Cleaner Output

If you want to ensure that the output is clean and devoid of unnecessary spaces, you can use the following XPath expression:

[[See Video to Reveal this Text or Code Snippet]]

The normalize-space() function cleans up any leading or trailing spaces, ensuring that you get a neat output of just 2.

Why the Issue with /p/text()?

When you attempted to use /p/text(), it failed once there was a space between <p> and <em>. Here's why:

The <p> element now has two text nodes as children; one that contains the space and the other that contains 2.

Thus, /p/text() would return a node set with both text nodes, rather than a single focused output.

Summary of Solutions

Use /p/em/following-sibling::text() to select the text node after the <em> tag.

Use normalize-space(/p/em/following-sibling::text()) to strip out unwanted spaces and get the exact text value.

Conclusion

XPath can be tricky when dealing with text nodes outside tags, but with the right syntax and understanding, you can successfully extract what you need. By following the steps provided in this post, you can confidently retrieve standalone text values in your XML or HTML documents. Always remember to consider spaces and siblings in your XPath queries to ensure accurate results!

If you have any questions or further challenges with XPath, feel free to reach out or leave a comment below!