How to write regexp?

how to write regexp in Jquery

i.e. Var regexp = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/开发者_开发百科;

if there is any syntax to write the expression..

can any one help me, how to write and if u know any useful site share with meee..

you can either write

var pattern = /abc/[modifiers];

or

var pattern = new Regex("abc",[modifiers]);