Photoshop script to replace a smart object within a PSD with selected image(s) and save result as a JPG. (Transformations to the smart object will be applied to new images).

replace_smartobject_image.js

// Replace SmartObject’s Content and Save as JPG
// 2017, use it at your own risk
// Via @Circle B: https://graphicdesign.stackexchange.com/questions/92796/replacing-a-smart-object-in-bulk-with-photoshops-variable-data-or-scripts/93359
// JPG code from here: https://forums.adobe.com/thread/737789

#target photoshop
if (app.documents.length > 0) {
    var myDocument = app.activeDocument;
    var theName = myDocument.name.match(/(.*)\.[^\.]+$/)[1];
    var thePath = myDocument.path;
    var theLayer = myDocument.activeLayer;
    // JPG Options;
    jpgSaveOptions = new JPEGSaveOptions();  
    jpgSaveOptions.embedColorProfile = true;  
    jpgSaveOptions.formatOptions = FormatOptions.STANDARDBASELINE;  
    jpgSaveOptions.matte = MatteType.NONE;  
    jpgSaveOptions.quality = 8;   
    // Check if layer is SmartObject;
    if (theLayer.kind != "LayerKind.SMARTOBJECT") {
        alert("selected layer is not a smart object")
    } else {
        // Select Files;
        if ($.os.search(/windows/i) != -1) {
            var theFiles = File.openDialog("please select files", "*.psd;*.tif;*.jpg", true)
        } else {
            var theFiles = File.openDialog("please select files", getFiles, true)
        };
        if (theFiles) {
            for (var m = 0; m < theFiles.length; m++) {
                // Replace SmartObject
                theLayer = replaceContents(theFiles[m], theLayer);
                var theNewName = theFiles[m].name.match(/(.*)\.[^\.]+$/)[1];
                // Save JPG. If you have need of saving different artboards into separate files,
                // see https://gist.github.com/laryn/0a1f6bf0dab5b713395a835f9bfa805c#gistcomment-3996733
                myDocument.saveAs((new File(thePath + "/" + theName + "_" + theNewName + ".jpg")), jpgSaveOptions, true,Extension.LOWERCASE);
            }
        }
    }
};
// Get PSDs, TIFs and JPGs from files
function getFiles(theFile) {
    if (theFile.name.match(/\.(psd|tif|jpg)$/i) != null || theFile.constructor.name == "Folder") {
        return true
    };
};
// Replace SmartObject Contents
function replaceContents(newFile, theSO) {
    app.activeDocument.activeLayer = theSO;
    // =======================================================
    var idplacedLayerReplaceContents = stringIDToTypeID("placedLayerReplaceContents");
    var desc3 = new ActionDescriptor();
    var idnull = charIDToTypeID("null");
    desc3.putPath(idnull, new File(newFile));
    var idPgNm = charIDToTypeID("PgNm");
    desc3.putInteger(idPgNm, 1);
    executeAction(idplacedLayerReplaceContents, desc3, DialogModes.NO);
    return app.activeDocument.activeLayer
};

@kakachiex2

Wow that looks really great! I have not expanded my knowledge into uxp yet. Have looked at it a couple times. A new language always seems very daunting. Plus it was still lacking many features back then. Is everything possible now like with jsx and in terms of executing app commands as well?