SP2013: Get path of current listItem in Javascript/CSOM?

Question

I am customize the DispForm.aspx with some javascript code. I would like to get in javascript the path of the current listitem. How can I do that?

UPDATE:

I have now this code to get the path/url of the current listItem. Is it OK or can it be better?

                // get list ID
                var listId = _spPageContextInfo.pageListId;
                var cleanListId = listId.replace('{','').replace('}','');

                // get item ID
                JSRequest.EnsureSetup(); 
                var itemid = JSRequest.QueryString["ID"];

                // get current site collection url
                var currentSiteCollectionFullUrl = window.location.protocol + '//' + window.location.host + _spPageContextInfo.siteServerRelativeUrl;

                // generate path of current listitem
                var path = currentSiteCollectionFullUrl + '_layouts/15/listform.aspx?PageType=4&ListId=' + cleanListId + '&ID=' + itemid;

Answer 1

How to get List Item Id in Display Form page:

//Source: http://stackoverflow.com/a/901144/1375553
function getParameterByName(name) {
    name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
    var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
        results = regex.exec(location.search);
    return results == null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
}

var listItemId = parseInt(getParameterByName('ID'));
console.log(listItemId);

Answer 2

You may like to use the information stored in _spPageContextInfo. It contains information about list item Id, List id etc. Example:

 _spPageContextInfo 
{
    webServerRelativeUrl : "/ProjectWeb",
    webLanguage : 1033,
    currentLanguage : 1033,
    webUIVersion : 4,
    pageListId : "{c1d7b89f-f07b-4e2e-b89c-76c315831d59}",
    pageItemId : 5,
    userId : 68,
    alertsEnabled : true,
    siteServerRelativeUrl : "/",
    allowSilverlightPrompt : "True"
} 

See this for more information: http://johnliu.net/blog/2012/2/3/sharepoint-javascript-current-page-context-info.html

UPDATE

Just checked it using View source of display page. pageItemId is not present there. However, you can use SharePoint’s GetUrlKeyValue() function to get item id. Example:

var thisItemId = GetUrlKeyValue("ID", false, location.href);