JavaScript | Regular expressions Advanced

To implement regular expressions in JavaScript:
str.replace(/[0-9]/gi,"a");
If the str contains ab09, then the above function will return str=abaa
Regular expressions are used in pattern matching, i.e., to find if a particular pattren exists in a string. It takes optional parameters 'g' and 'i':-

Every regular expression has two properties:-

1. g - It specifies that all the matching characters should be replaced. If g is not specified only the first matching character will be replaced
2. i - The i stands for ignore case
   i.e., if the regular experession is /[a-c]/i,"d"
   then the str="aAbBcC" will be transforemed to Str="dddddd Both the lowercase and uppercase characters will be transformed. If i is not specified, only the lowercase charcaters will be transformed. for example, if regular expression is /[a-c]/, then the string will become "dAdBdC".

[0-9]:- matches all single numeric charcters
[abc]:- matches one of "a","b","c" characters

trim() function:

To remove the unwanted regular expressions from the left and right ends of a string, we use str.trim()
for example,
if str=" gaurav ";
then str.trim() will return str="gaurav";