Reference type-RegExp type

JavaScript Advanced Programming (3rd Edition) Notes-Chapter 5-RegExp Types

There are two ways to define regular expressions

1. Define regular expressions in literal form:

ver expression = /patterns/flags;

patterns: can be any simple or complex regular expression

flags:

g: global

i: means case insensitive

m: indicates multi-row mode, which continues to find the next row when it reaches the end of one row

var patterns1 = /at/g;//matches all instances of "at" in characters var patterns2 = /[bc]at/i;//matches all "bat" or "cat", case insensitive var patterns3 = /.at/gi;//matches all combinations of three characters ending in "at", case insensitive

All metacharacters used in patterns must be escaped, metacharacters in regular expressions include: ( [ { \ ^ $| ) ? * + . ] }

var patterns4 = /\[bc\]at/i;//matches the first "[bc]at", case insensitive

2. Define a regular expression with RegExp constructor, which accepts two parameters (patterns,flags)

var patterns2 = new RegExp("[bc]at","i");//Same as var patterns2 = /[bc]at/i;

Also use RegExp to escape metacharacters and double escape

vqr patterns 4 = new RegExp("\\[bc\\]at","i"); Same as var patterns4 = /\[bc\]at/i;

These two methods create different regular expressions. Regular expression literals always share a RegExp instance, and each new RegExp instance created using a constructor is a new instance

var re = null, i; for(i=0;i