regEx to find a dynamic substring in a string

Question

I have a string which contains a markup. Inside the markup there is an identifier/or substring which I want to pick which would look like this

ghost://{schema_name}/{id}

as an example

 ghost://blogging/232323

Note: if required, we can change the identifier to something we can find more easily in our string.

Consider this as a string

const somesting = `
<h1> Random Heading </h1> 
<p> Random Text </p> 
<p> a href="ghost://blogging/232323"> Text I want to pick </a> </p>
`

Here, I want to pick ghost://blogging/232323 and change it to an actual link.

From googling, I found that I can achieve this by using grammar but I am not sure how to write grammar/regular expression here (or any other way)

Would so appreciate if anyone could help me out.

Based on the answer by CertainPerformance, I did this but unfortunately this isn't working

const somesting = `
<h1> Random Heading </h1> 
<p> Random Text </p> 
<p> a href="ghost://xman-article/HPHvLTH06YUMfdMnokOl/spaceyfi-product-launch"> Text I want to pick </a> </p>
`;

const replaced = somesting.replace(
  /ghost:\/\/(\w+)\/(\d+)/g,
  (_, schema_name, id, slug) => `/${schema_name}/${id}/${slug}`
);

console.log(replaced)

What do you mean by grammar?

yqlim
– yqlim

2019-12-31 03:57:50 +00:00
Commented Dec 31, 2019 at 3:57 — yqlim
– yqlim, Commented Dec 31, 2019 at 3:57

CertainPerformance · Accepted Answer · 2019-12-31 06:32:57Z

2

You can use a regular expression to match ghost://, followed by word characters (or whatever characters are permitted for the schema name), followed by another slash and number. Here's an example of how you'd dynamically replace that with a href="https://blogging.com/article/232323":

const somesting = `
<h1> Random Heading </h1> 
<p> Random Text </p> 
<p> a href="ghost://blogging/232323"> Text I want to pick </a> </p>
`;

const replaced = somesting.replace(
  /ghost:\/\/(\w+)\/(\d+)/g,
  (_, schema_name, id) => `https://${schema_name}.com/article/${id}`
);
console.log(replaced);

The schema name and id are variables inside the .replace callback, so feel free to use them however you need to there, and return the string to be replaced at the end of the callback.

If you have a third part of the ghost that you need to capture, then make a third capturing group so that the fourth parameter to the .replace callback can see it:

const somesting = `
<h1> Random Heading </h1> 
<p> Random Text </p> 
<p> a href="ghost://xman-article/HPHvLTH06YUMfdMnokOl/spaceyfi-product-launch"> Text I want to pick </a> </p>
`;

const replaced = somesting.replace(
  /ghost:\/\/([^/]+)\/([^/]+)\/([^"])/g,
  (_, schema_name, id, slug) => `/${schema_name}/${id}/${slug}`
);

console.log(replaced)

edited Dec 31, 2019 at 6:32

answered Dec 31, 2019 at 3:59

CertainPerformance

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2 Comments

Alwaysblue Over a year ago

Thanks a lot for answering, update the snippet which I tried and isn't working

CertainPerformance Over a year ago

If you want to be able to use another parameter, you'll need to capture another group in the pattern. It's not clear, but you might not actually need to capture these - if you just need the whole string past the ghost, but not the individual elements of it, you can just use one capture group around everything after ghost instead.

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