Get All Item Of Library or List in All Folder Using Rest Api (recursivily)/ Using Caml query

function GetAllFoldersofRam()

{

var thisUrl = _spPageContextInfo.webAbsoluteUrl + "/_api/web/lists/getbytitle('NGO-DCUMENT)/GetItems"; 

var caml = '<View Scope="Recursive"><Query><ViewFields><FieldRef Name="Name" /></ViewFields> </Query></View>'; 

$.ajax({ 

    url: thisUrl, 

    type: "POST",

    async: false, 

    headers: { 

        "Accept": "application/json; odata=verbose", 

        "X-RequestDigest": $("#__REQUESTDIGEST").val(), 

        "Content-Type": "application/json; odata=verbose" 

    }, 

    data: JSON.stringify({"query": { "__metadata": { "type": "SP.CamlQuery" }, "ViewXml": caml}}),           

    success: function (data){ 

    alert(data.d.results.length);

        // data.d will yield the required results 

    }, 

    error: function (data){ 

        console.log("Error in query");           

    } 

}); 

}

Useful Link:

https://platinumdogs.me/2009/07/21/querying-document-libraries-or-pulling-teeth-with-caml/

http://www.c-sharpcorner.com/blogs/filter-documents-from-sharepoint-libraries-by-metadata-using-rest-api