Convert Flat to Nested Data Structure

nest.cfm

<cfscript>

function groupBy( collection, callback ) {
    var grouping = {};
    for ( var item in collection ) {
        var key = callback( item );
        if ( ! grouping.keyExists( key ) ) {
            grouping[ key ] = [];
        }
        grouping[ key ].append( item );
    }
    return grouping;
}

function nest( collection, nestingKey ) {
    var grouped = groupBy( collection, function( item ) {
        return item[ nestingKey ];
    } );
    
    var baseGroup = grouped[""];

    return nestSlice( baseGroup, grouped );
}

function nestSlice( slice, collection ) {
    if ( slice.isEmpty() ) {
        return slice;
    }
    
    return slice.map( function( item ) {
        return {
            id = item.id,
            nodeText = item.nodeText,
            children = nestSlice( collection[ item.id ] ?: [], collection )
        };
    } );
}

// Test data
TestData = querynew("id,parentId,nodeText");
queryAddRow(TestData,{id:1,nodeText:"File" });
queryAddRow(TestData,{id:2,nodeText:"New",parentId:1});
queryAddRow(TestData,{id:3,nodeText:"File",parentId:2});
queryAddRow(TestData,{id:4,nodeText:"Folder",parentId:2});
queryAddRow(TestData,{id:5,nodeText:"Edit"});
queryAddRow(TestData,{id:6,nodeText:"Copy",parentId:5});
queryAddRow(TestData,{id:7,nodeText:"Cut",parentId:5});
queryAddRow(TestData,{id:8,nodeText:"Paste",parentId:5});
queryAddRow(TestData,{id:9,nodeText:"Help"});
queryAddRow(TestData,{id:10,nodeText:"About",parentId:9});


writeDump( nest( TestData, "parentId" ) );

</cfscript>