object traversal optimization and indexing

chords.js

var notes = [{
    "note": "A",
    "chords": [
        {
            "chord": "maj7",
            "strings": {
                "1": 0,
                "2": 3,
                "3": 2,
                "4": 0,
                "5": 1,
                "6": 2
            }
        },
        {
            "chord": "min",
            "strings": {
                "1": 0,
                "2": 3,
                "3": 2,
                "4": 0,
                "5": 1,
                "6": 2
            }
        }
    ]
},{
    "note": "B",
    "chords": [
        {
            "chord": "maj7",
            "strings": {
                "1": 0,
                "2": 3,
                "3": 2,
                "4": 0,
                "5": 1,
                "6": 2
            }
        },
        {
            "chord": "min",
            "strings": {
                "1": 0,
                "2": 3,
                "3": 2,
                "4": 0,
                "5": 1,
                "6": 2
            }
        }
    ]
}];


// corrected and optimized original getChord implementation
function getChord( myNotes, theNote, theChord ) {
    var i = myNotes.length,
        notesObj, theChords, j;
    while(i--) {
        notesObj = myNotes[i];
        if (notesObj.note == theNote) {
            theChords = myNotes[i].chords;
            var j = theChords.length;
            while(j--) {
                chordObj = theChords[j]
                if (chordObj.chord == theChord) {
                    return chordObj.strings;
                }
            }
        };
    }
}


// build chord/note index
function buildChordIndex( myNotes ) {
    var chordIndex = [],
        i = myNotes.length,
        noteObj, note, chordList, j, chordObj, chord;
    while (i--) {
        noteObj = myNotes[i];
        note = noteObj.note;
        chordList = noteObj.chords;
        j = chordList.length;
        while(j--) {
            chordObj = chordList[j];
            chord = chordObj.chord;
            // assumes standard 12 notes for efficiency, should be no conflict
            // but add a separator if necessary
            chordIndex[ note + chord ] = [ i, j ];
        }
    }
    return chordIndex;
}

// uses the index instead of traversing
function getChordIndexed( myNotes, myIndex, theNote, theChord ) {
    var indexValue = myIndex[theNote + theChord];
    return myNotes[ indexValue[0] ].chords[ indexValue[1] ].strings;
}

console.log( getChord( notes, "A", "maj7" ) );

var chordIndex = buildChordIndex(notes);
console.log( getChordIndexed( notes, chordIndex, "A", "maj7" ) );