Скачать или смотреть Extracting string instances in URLs from HTML with JavaScript

Learn how to efficiently extract all instances of specific strings in URLs embedded in HTML using JavaScript. Simplify your code and make it memory efficient!
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This video is based on the question https://stackoverflow.com/q/73121703/ asked by the user 'Wojtek Zeglin' ( https://stackoverflow.com/u/2294140/ ) and on the answer https://stackoverflow.com/a/73122467/ provided by the user 'David Machado' ( https://stackoverflow.com/u/9076558/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Extracting Instances of a String Within URLs in HTML using JavaScript

Extracting specific data from a large HTML file can be a daunting task, especially when dealing with strings embedded within complex structures like URLs. In this post, we’ll explore how to efficiently extract all instances of a particular string found between specified segments of URLs within an HTML context.

The Challenge

Imagine you have a sizeable HTML file (around 50MB), and you want to extract unique identifiers from URLs. The URLs often contain slashes, making it tricky to pinpoint where your string starts and ends. Here's an example of what you're likely dealing with:

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

Desired Outcome

Your goal is to extract identifiers like 091209283 and 091209284 from the URLs. Different functions and methods you may have tried to accomplish this task might consume excessive memory, especially for large files.

A JavaScript Solution

We can craft a JavaScript function that utilizes character iteration instead of relying on heavy regex operations. This approach is not only more efficient but also less memory-intensive for large files.

Step-by-step Breakdown

Function Setup: We’ll create a function named findIds that utilizes two key parameters - the beginning and ending strings to delineate what we’re looking for.

Character Iteration: Instead of splitting the string multiple times or using regex, we'll iterate over each character of the URL string.

Matching Logic: As we iterate, we’ll check for matches with the beginning string and, upon finding one, we’ll look for the ending string to capture the required content.

Here's how the function looks:

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

Explanation of the Code

Initialization: Convert your before and line variables into arrays. This makes accessing individual characters easier.

Accumulate Results: We create an empty array to store our results.

Character Matching: We compare each character in the line with the characters in the before string. If they match, we start collecting the characters until we reach the end string.

Final Output: The function returns an array containing the extracted identifiers.

Conclusion

When encountering a need to extract specific strings from HTML-styled URLs, this JavaScript function provides an efficient, memory-friendly approach. With clear markers to define where to start and stop, this method minimizes complexity while effectively providing the desired output.

By iterating through each character rather than employing complex regex patterns, you're able to handle even large files without exorbitant memory consumption. Try implementing this in your projects and enjoy the efficiency!

If you have any questions or need further assistance, feel free to leave a comment!