HOw to Get current Item ID in Editform or Display Form In SharePoint list Default forms?

In this below script,Get current Item ID in Editform or Display Form In SharePoint list Default forms

function GetID()
{
var getid = new RegExp("[\\?&]"+"ID"+"=([^&#]*)");
 value = getid.exec(window.location.href);
alert(value[1]);

}

_spBodyOnLoadFunctionNames.push("GetID");