Need to replace an image with an image from a URL using extendscript

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@LiamR36 wrote:

but it gives me an error when I try and convert a layer to a smart object like this:

whateverLayer.kind = LayerKind.SMARTOBJECT

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As you have found, that isn't valid code.

To convert an active layer to a smart object:

// Convert layer to smart object
var convertToSmartObject = stringIDToTypeID("newPlacedLayer");
executeAction( convertToSmartObject, undefined, DialogModes.NO );

Or perhaps:

// Convert layer to smart object
var savedDisplayDialogs = app.displayDialogs;
app.displayDialogs = DialogModes.NO;
app.runMenuItem(stringIDToTypeID('newPlacedLayer'));
app.displayDialogs = savedDisplayDialogs;

Just delete the layer, create a new one, and paste in the image.

This would convert the active Layer/s to one Smart Object. 

////// convert to smart object //////
function convertToSmartObject () {
var desc108 = new ActionDescriptor();
var ref77 = new ActionReference();
ref77.putEnumerated( charIDToTypeID( "Mn  " ), charIDToTypeID( "MnIt" ), stringIDToTypeID( "newPlacedLayer" ) );
desc108.putReference( charIDToTypeID( "null" ), ref77 );
executeAction( charIDToTypeID( "slct" ), desc108, DialogModes.NO );
};