Today I explore with Javascript regular expression. It is interesting. I have added below what I learned so far.
You have to put regular expression syntax is of two slashes. Like this /hello/. if you include i after that it will escape case sensitivity. for example /hello/i.
Here is some function that works on regular expression:
- exec() : Return result in an array or null
- test() : Retun result true or false
- match() : Its works same as exec(). dffterent between exec and match is exec show result on only first match found and match shows all of them.
- search(): Return index of the first match if not found return -1
let re;
re = /hello/;
re = /hello/i;
const content = 'Hello there, is it 2449? Bangladesh';
re.test(content); // const resultContent =
console.log(resultContent);
How it works:
- /^h/i < search start with character h
- /wrold$/ : the content must end with world world
- /^hello$/ : The word must begin and end with hello
- /h.llo/ : It will matches any one character.
- /h*llo/ : It will matches any charter 0 or more time on the content.
- /gre?a?y/ : Its works as optional if any word has a or e it will work on that.
- /gre?a?y\?/ : The backslash use for escape optional.
Use of Brackets on Regular expression:
- /gr[ae]y/ : It will match same as before any one character. like a or e.
- /[GF]ray/ : must be a G or F
- /^[GH]/ : match anything except G and F
- /[A-Z]/ : match any uppercase letter
- /[a-z]/ : match any lowercase letter
- /[A-Za-z]/ : match any letter.
- /[0-9]/ : match any digit.
Quantifiers on Regular Expression:
Type a letter more than one or a custom time we use qualifiers. here is how to use that:
- /hel{2}o/ : Must l need to occur exactly {mentioned} amount of time
- /hel{2,4}o/ : Must l need to occur 2-4 amount of time. more than that or less than that will not work.
- /hell{2,}o/ : in this case, l can occur 2 to an infinite amount of time.
- /^([0-9]x){3}/ : this grouping . if i want 3x3x3x than this will work fine.
Regular expression shorthand character classes
- /\w/ : will support alphabetic and numeric or _ characters. only the first character will match.
- /\w+/ : It Will add one more letter. All the characters will show.
- /\W/ : Used in for non words letter.
- /\d/ : It will match only numbers only. no characters will match on this.
- /\d+/ : If u want to show one or more letters this will work fine.
- /\D/ : numbers will not match on this. only character.
- /\s/ : Count space as a character.
- /\S/ : non-whitespace character will show. whitespace will not count.
- /hell\b/ : word boundary. If you want to search full word, not a 2-3 charter match uses this. For example, “Hello, I am at hell”. in this case it will escape ‘hello’ and count the ‘hell’.
- /x(?=y)/ : assertions work as conditions. for this, it will only match if the character found ‘xy’.
- /x(?!y)/ : assertions work as conditions. for this, it will only match if the character found that not followed by ‘xy’.
I hope you enjoy this post. Thanks.
