Regular expression to get a string between two strings in Javascript

How to Get a String Between Two Strings in JavaScript: Demystifying Regular Expressions

Are you tired of struggling to extract a specific string from another string in JavaScript? Do regular expressions make your brain feel like it's doing acrobatics? Fear not! In this blog post, we will dive into the world of regular expressions and unveil the secret to getting a string between two strings. 🎩🐇

The Problem: Getting a String Between "Cow" and "Milk"

Picture this: you stumble upon a paragraph and your mission is to extract the juicy string hidden between the words "cow" and "milk". 🥛🐄

Let's take a look at our starting point:

<p>My cow always gives milk</p>

And our desired output:

"always gives"

The Failed Attempt: A Common Mistake

Like any brave coder, you roll up your sleeves and give it your best shot. After some puzzling, you come up with the following regular expression:

/(?=cow).*(?=milk)/

However, upon testing, you end up with the undesired result: "cow always gives". 😱

The Solution: Using Non-Greedy Matching

So, what went wrong? The asterisk (*) quantifier in regular expressions is greedy by default. It matches as much as it can. In our case, it means it would match everything between the first occurrence of "cow" and the last occurrence of "milk".

To solve this, we need to make the quantifier non-greedy. We can achieve this by adding a question mark (?, how ironic!) after the asterisk, like this:

/(?=cow).*?(?=milk)/

Now, let's put our newfound knowledge to the test!

Putting It into Action: Extracting the Desired String

By incorporating the non-greedy matching technique, our regular expression becomes:

/(?=cow).*?(?=milk)/

Let's use this expression in JavaScript code to get our desired output:

const input = "My cow always gives milk";
const regex = /(?=cow).*?(?=milk)/;
const result = input.match(regex)[0];

console.log(result);
// Output: "always gives"

Voilà! 🎉 We successfully extracted the desired string "always gives" using our modified regular expression.

Take It to the Next Level: Make It Dynamic

But wait, there's more! What if you want to extract a string between different starting and ending strings? Fear not, because our solution is dynamic and versatile.

Simply replace "cow" and "milk" in our regular expression with your desired starting and ending strings. For example:

const input = "I want to extract this string. Start here and end there.";
const startString = "Start here";
const endString = "end there";

const startRegex = new RegExp(`(?=${startString}).*?`);
const endRegex = new RegExp(`(?<=${endString})`);

const result = input.replace(startRegex, "").replace(endRegex, "");

console.log(result);
// Output: "I want to extract this string."

Now you can extract strings like a pro, regardless of the starting and ending strings you desire. 🌟

Stay Curious, Keep Learning

Regular expressions can be intimidating, but with practice and a little creativity, they become a powerful tool in your coding arsenal. 😎

Now that you've conquered the world of getting a string between two strings, let your imagination run wild! Start exploring more advanced regex patterns and bring your coding skills to the next level.

Got any tricky regex questions or cool regex tricks to share? We'd love to hear from you in the comments below! Let's continue this regex adventure together. 💪💬

Keep coding and stay curious! ✨