Regular expressions provide a powerful way to search and manipulate text. If you're familiar with SQL, you can think of regular expressions as being somewhat similar to SQL: you use SQL to find and update data inside a database, and you use regular expressions to find and update data inside a piece of text.
"regular expression" is often shorten and called as "regex" or "regexp".
A regular expression consists of:
var re = new RegExp("j.*t");
There is also the more convenient regexp literal:
var re = /j.*t/;
In the example above, j.*t is the regular expression pattern. It means, "Match any string that starts with j, ends with t and has zero or more characters in between". The asterisk * means "zero or more of the preceding"; the dot (.) means "any character". The pattern needs to be placed in quotation marks when used in a RegExp() constructor.