Why regular expressions

An example of a matching word is "tsakeha". You can use this expression in case you want to search for annotations ending with a "g", but not with "ng". In Dutch, you will find "snelweg" and "maandag" as the results but not words as "bang". You can use this expression if you want to search for annotation starting and ending with "k" and with one or more character between them, e.

The pattern also work with attribute of the following input types: text, date, search, url, tel, email, and password. Now that you have a better understanding of what RegEx is, when should you use it?

Though this is the beginning of your RegEx journey, I highly implore you to just go out there and get stuck in. You could even do something similar to the signup validation demo I did below?

So I created a demo for this article that outlines how to hypothetically use regEx on a sign up form and check for validation without a regEx library. If you liked what I wrote you can find me on twitter or on medium. I love what I do, what I learn and sharing it with others. Coding tutorials and news. The developer homepage gitconnected. Sign in. Harry Ghazni Follow. The common explanation is: Regular Expressions is a sequence of characters that define a search pattern.

Wanna learn some fun tricks? Good use cases Throwaway code User-input validation When trying to find a specific pattern within a big glob of text! Most standard libraries have mature tools for pulling a URL apart into its own corresponding parts.

Here is an example of the hoops you have to jump through with regex to parse most not all valid email addresses. Once remembered, the substring can be recalled for other use. See Groups and ranges for more details. Regular expressions are used with the RegExp methods test and exec and with the String methods match , replace , search , and split.

When you want to know whether a pattern is found in a string, use the test or search methods; for more information but slower execution use the exec or match methods. If you use exec or match and if the match succeeds, these methods return an array and update properties of the associated regular expression object and also of the predefined regular expression object, RegExp.

If the match fails, the exec method returns null which coerces to false. In the following example, the script uses the exec method to find a match in a string. If you do not need to access the properties of the regular expression, an alternative way of creating myArray is with this script:.

See Using the global search flag with exec for further info about the different behaviors. If you want to construct the regular expression from a string, yet another alternative is this script:. With these scripts, the match succeeds and returns the array and updates the properties shown in the following table.

As shown in the second form of this example, you can use a regular expression created with an object initializer without assigning it to a variable. If you do, however, every occurrence is a new regular expression. For this reason, if you use this form without assigning it to a variable, you cannot subsequently access the properties of that regular expression. For example, assume you have this script:.

If you need to access the properties of a regular expression created with an object initializer, you should first assign it to a variable. Regular expressions have optional flags that allow for functionality like global searching and case-insensitive searching. These flags can be used separately or together in any order, and are included as part of the regular expression.

Note that the flags are an integral part of a regular expression. They cannot be added or removed later. The m flag is used to specify that a multiline input string should be treated as multiple lines. The syntax looks so frustrating, and I thought I would never learn anything about it. This happens to us all. Luckily I found good online resources back then and started to really dig into it. The results were remarkable, and now I use it every day.

It serves as a great tool to boost up my workflow. Do not be afraid. Following my internship, I came upon to a situation where I had to write some Go code which has a struct of many fields. Sample file:. To follow my task I had to add transform above into something similar below.

Yes, we can also copy one JSON tag and paste it right next changing the name to yaml. But when there are multiple fields, this task is pretty boring and also error-prone. Since this is a tedious task, I decided to use my knowledge of Regex to save me. I needed find every field with a json prefix and paste them with yaml. So I opened my IDE and typed the following. This is a grumpy regex statement.

What it does as follows. As you can see all the information we need is captured.