Help With Including Curves Changes In Script

Hey ian-barber​, you're right. I missed the fact that different document modes require a different charID. Here's the updated function which will work on any document mode. I'm pretty sure I covered all of them, including all possible monotone / duotone / tritone / quadtone options.

// Examples  
var point1 = [28, 0];  
var point2 = [37, 90];  
var point3 = [163, 155];  
var point4 = [253, 190];  
  
// Add points to array  
var points = [point1, point2, point3, point4];  
  
// Execute  
modifySelectedCurvesLayer(points);  
  
/* 
 * @param {Array} points 
 * --> forEach : [x, y] 
 */  
function modifySelectedCurvesLayer(points) {
    // Validate input
    if(points.length < 2) {   
        alert('Curves need a minimum of 2 points');  
        return false;  
    }
    
    // Analyze document mode
    switch(app.activeDocument.mode.toString()) {
        case "DocumentMode.RGB":
        case "DocumentMode.CMYK":
            var docModeCharID = "Cmps";
            break;
    
        case "DocumentMode.GRAYSCALE":
            var docModeCharID = "Blck";
            break;
            
        case "DocumentMode.DUOTONE":
            var channelName = app.activeDocument.channels[0].name;
        
            if( channelName == "Monotone" ) {
                var docModeCharID = "Mntn";
            } else if( channelName == "Duotone" ) {
                var docModeCharID = "Dtn ";
            } else if( channelName == "Tritone" ) {
                var docModeCharID = "Trtn";
            } else if( channelName == "Quadtone" ) {
                var docModeCharID = "Qdtn";
            }
            
            break;
            
        case "DocumentMode.LAB":
            var docModeCharID = "Lght";
            break;
            
        default: 
            break;
    }
      
    var desc = new ActionDescriptor();  
    var ref = new ActionReference();  
        ref.putEnumerated( charIDToTypeID( "AdjL" ), charIDToTypeID( "Ordn" ), charIDToTypeID( "Trgt" ) );  
        desc.putReference( charIDToTypeID( "null" ), ref );  
      
    var curvesLayerDesc = new ActionDescriptor();  
        curvesLayerDesc.putEnumerated( stringIDToTypeID( "presetKind" ), stringIDToTypeID( "presetKindType" ), stringIDToTypeID( "presetKindCustom" ) );  
      
    var chnlList = new ActionList();  
    var chnlDesc = new ActionDescriptor();  
    var channelRef = new ActionReference();  
        channelRef.putEnumerated( charIDToTypeID( "Chnl" ), charIDToTypeID( "Chnl" ), charIDToTypeID( docModeCharID ) );  
        chnlDesc.putReference( charIDToTypeID( "Chnl" ), channelRef );  
      
    var pointsList = new ActionList();  
      
    for(var i = 0; i < points.length; i++) {  
        var pointDesc = new ActionDescriptor();  
            pointDesc.putDouble( charIDToTypeID( "Hrzn" ), points[0] );  
            pointDesc.putDouble( charIDToTypeID( "Vrtc" ), points[1] );  
            pointsList.putObject( charIDToTypeID( "Pnt " ), pointDesc );  
    }  
      
        chnlDesc.putList( charIDToTypeID( "Crv " ), pointsList );  
        chnlList.putObject( charIDToTypeID( "CrvA" ), chnlDesc );  
      
        curvesLayerDesc.putList( charIDToTypeID( "Adjs" ), chnlList );  
        desc.putObject( charIDToTypeID( "T   " ), charIDToTypeID( "Crvs" ), curvesLayerDesc );  
    executeAction( charIDToTypeID( "setd" ), desc, DialogModes.NO );  
}