SP.ClientContext.get_current() undefined

Error: SP.ClientContext.get_current() undefined

Error:The value of the property 'ExecuteOrDelayUntilScriptLoaded' is null or undefined, not a Function object
SP.ClientContext.get_current() undefined
SP undefined

If you get any error..

Solution:

<SharePoint:ScriptLink ID="ScriptLink1" Name="SP.js" runat="server" OnDemand="false" LoadAfterUI="true" Localizable="false"></SharePoint:ScriptLink>
<SharePoint:FormDigest runat="server"/>

Add above tags inside form