Regex Regular Expression Javascript

Regex

Regular Expression - Tech and Technology

Regex

What is RegEx? RegEx means Regular Expression, it is used JavaScript and other Platforms and Programming Languages.
Example in javascript: var regex = /[A-Za-z0-9]/;

The / and / characters are used to start and end the regular expression.

The //ig : ig means global replace

[A-Z] Matches any uppercase character from A to Z .

[0-9] Matches any whole numbers from 0 to 9 .

/[^0-9]/ not a digit

[a-zA-Z0-9] Matches any character from a to z or A to Z or 0 to 9 .

[^abc] Matches any character except a , b or c .

[] The square brackets are used to match any one of multiple specified patterns.

\w which is equivalent to RegEx \[A-Za-z0–9_]\

\W To skip all numbers and letters

\d To match only digits

\D To not match digits

$ character matches the end of the string.

/^[A-Za-z0-9]*$/

/^[a-z0-9]+$/i

\s is a whitespace, in a regular expression matches any one of the characters: space, formfeed ( \f ), newline ( \n ), return ( \r ), tab ( \t ), vertical tab ( \v ), non-breaking space ( \xA0 ), as well as the Unicode characters \u00A0 \u2028 \u2029 .

The ^ character matches the beginning of the string,

The RegExp test() method searches for a match between the regular expression and a specified string.

The * character matches zero or more occurrences of a particular pattern. We add it after the square brackets to match any of the patterns in the brackets as many times as possible.

The String replace() method returns a new string with some or all matches of a specified pattern replaced by a replacement. We use an empty string ('') as the replacement to have all the letters and numbers removed in the resulting string.

We use the g (global) flag to match all the occurrences of the pattern in the string. If we don’t specify this flag, only the first match of a letter or number will be removed.

We pass the result of match() to the Boolean constructor to convert it to a Boolean. Boolean() converts truthy values to true, and falsy values to false.

In JavaScript, there are six falsy values: undefined, null, NaN, 0, '' (empty string), and false. Every other value is truthy.

Example in javascript:

 
var myString = ' Title  Number=123 Character=ABC or programs if (x>0) {j = c;}';
var myResult = myString.replaceAll(/[^A-Za-z0-9_-áéíóúñ]/ig, '');
console.log(myResult.replace(/[A-Za-z0-9]/g, ''));


// is the same
const myRegex = /\w+/;
// OR
const myRegex = new RegExp("\\w+");