Various snippets for selecting a single Photoshop layer

Select a single layer.jsx

/* Presuming that a layer has a unique name (otherwise the first layer with the name will be targeted) */

var selectLayer1 = app.activeDocument.artLayers.getByName("Layer 1");
app.activeDocument.activeLayer = selectLayer1;
 

/* or */

app.activeDocument.activeLayer = app.activeDocument.layers["Layer 1"];


/* The layers collection can also be used, indexing starts at zero, so the 8th layer from the top would be 7 */

var selectLayer = app.activeDocument.layers[7];
app.activeDocument.activeLayer = selectLayer;

/* or */

app.activeDocument.activeLayer = app.activeDocument.layers[7];
 

/* Select layer via static id value */

selectLayerById(1); // Enter layer.id number

function selectLayerById(id)
/* https://graphicdesign.stackexchange.com/questions/130739/photoshop-scripting-applying-changes-only-to-selected-artboards */
{
  var desc1 = new ActionDescriptor();
  var ref1 = new ActionReference();
  ref1.putIdentifier(charIDToTypeID('Lyr '), id);
  desc1.putReference(charIDToTypeID('null'), ref1);
  executeAction(charIDToTypeID('slct'), desc1, DialogModes.NO);
}


/* Select layer via index value, Background layer index starts at 0 - no Background starts at 1 */

selectLayerByIndex(8);

function selectLayerByIndex(index) {
/* https://github.com/ES-Collection/Photoshop-Scripts/blob/master/Remove%20Unused%20Layers.jsx */
    var ref = new ActionReference();
        ref.putIndex(charIDToTypeID("Lyr "), index);
        var desc = new ActionDescriptor();
        desc.putReference(charIDToTypeID("null"), ref );
        desc.putBoolean( charIDToTypeID( "MkVs" ), false );
        executeAction(charIDToTypeID("slct"), desc, DialogModes.NO );
}


/* Select the first layer [0] inside the second layer set [1] */

app.activeDocument.activeLayer = app.activeDocument.layerSets[1].layers[0];