It is also expressed as regex. Regular expression is the backbone of form validation. We can validate any form elements using it. Both client side and server side elements can be validated using it. It is used in various programming or scripting language like PHP, JAVASCRIPT, PYTHON, PERL, etc.

It starts with carat(^) and end with dollor($) sign. E.g.

• /^[0-9]/ means starts with digit ie. 0 to 9, but end can be any thing.
• /[0-9]$/ means starting can be any character but it should end with digits.
• /^[0-9]$/ means starting with digit and end with digits.

You can add/remove query string from URL without reloading page in javascript. Generally URL changes by page reloading. When URL changes page gets refresh and new content appears on page.

e.g. Go

Here when we click 'Go' it goes to new URL with query string.

HTML5 gave you facility to change URL using pushState function to change URL and append data using ajax.

e.g. history.pushState({state:1, rand: Math.random()}, '', "?page="+1);

history.pushState function is used to add history state. It takes three parameters: a state object, a title (which is currently ignored), and (optionally) a URL.

Javascript developer give lots of efforts to find different function regarding URL.

We have segregated all functions related to URL in single place for the ease of developers