BPMGrid.jsx

/* @lachrymaL_F
    BPM Grid -> Adobe After Effects
    03/25/2020 */
{
        function BPMGrid(thisObj) {
            function BPMGrid_buildUI(thisObj) {
                var mainPanel = (thisObj instanceof Panel) ? thisObj : new Window("palette", "BPM Grid Creator", undefined, {resizable: true, closeButton: true});

                res = "group{orientation:'column',\
                groupBPM: Group{orientation:'row',\
                BPMEntryDesc: StaticText{text:'BPM: '},\
                BPMEntry: EditText{text:'120'},\
                },\
                groupSpacing: Panel{orientation:'row',\
                spacingDesc: StaticText{text:'Spacing: '},\
                spacingNumer: EditText{text:'1'},\
                spacingDivText: StaticText{text:'/'},\
                spacingDenom: EditText{text:'4'},\
                },\
                groupButton: Panel{orientation:'row',\
                createButton: Button{text:'Create Grid'},\
                },\
                }";
                
                mainPanel.grp = mainPanel.add(res);

                mainPanel.grp.groupButton.createButton.onClick = function() {
                    var BPM = posNumParser(Number(mainPanel.grp.groupBPM.BPMEntry.text));
                    var spacing = posNumParser(Number(mainPanel.grp.groupSpacing.spacingNumer.text)) / posNumParser(Number(mainPanel.grp.groupSpacing.spacingDenom.text));
                    createGrid(BPM, spacing);
                    }

                mainPanel.layout.layout(true);
                
                return mainPanel;
            }
        
            var myScriptPal = BPMGrid_buildUI(thisObj);
            
            if(myScriptPal != null && myScriptPal instanceof Window) {
                myScriptPal.center();
                myScriptPal.show();
            }
        }
    BPMGrid(this);
}

function posNumParser(inp) {
    if (inp !==  inp || inp <= 0) {
        alert('Please enter valid values!');
        throw 'Illegal Inputs!';
        }
    return inp
    }

function createGrid(BPM, spacing) {
        app.beginUndoGroup("Create BPM Grid");
        var BPMnull = app.project.activeItem.layers.addNull(app.project.activeItem.duration);
        BPMnull.name = "BPM Grid";
        BPMnull.source.name ="BPM Grid"
        var marginBetweenMarkers = (60 / BPM) * spacing;
        var finishLine = BPMnull.outPoint;
        for (var t = 0; t < finishLine; t =  t + marginBetweenMarkers){
            BPMnull.Marker.addKey(t);
            }
        BPMnull.locked = true;
        BPMnull.enabled = false;
        app.endUndoGroup();
    }