PhotoshopでsRGBのJPEGを一括保存するJSX｜上書き確認とエラー処理

#target photoshop
(function () {
    if (app.documents.length > 0) {
        alert("Save and close your open documents before running this script.");
        return;
    }
    var src = Folder.selectDialog("Select the input folder");
    if (!src) return;
    var dst = Folder.selectDialog("Select a separate, empty output folder");
    if (!dst) return;
    if (src.fsName.toLowerCase() === dst.fsName.toLowerCase()) {
        alert("Input and output folders must be different.");
        return;
    }
    var files = src.getFiles(function (f) {
        return f instanceof File && /\.(psd|tif|tiff|jpg|jpeg|png)$/i.test(f.name);
    });
    var targets = [], seen = {}, i;
    if (!files.length) { alert("No supported input files."); return; }
    for (i = 0; i < files.length; i++) {
        // Keep the original extension: sample.png.jpg and sample.psd.jpg.
        var target = new File(dst.fsName + "/" + decodeURI(files[i].name) + ".jpg");
        var key = target.fsName.toLowerCase();
        if (target.exists || seen[key]) {
            alert("Output already exists or is duplicated: " + target.fsName);
            return;
        }
        seen[key] = true;
        targets.push(target);
    }
    var opts = new JPEGSaveOptions();
    opts.quality = 10;
    opts.embedColorProfile = true;
    var saved = 0, failed = [], closeErrors = [];
    for (i = 0; i < files.length; i++) {
        var doc = null;
        try {
            if (targets[i].exists) throw new Error("Output appeared after the initial check.");
            doc = app.open(files[i]);
            if (doc.mode !== DocumentMode.RGB || doc.bitsPerChannel !== BitsPerChannelType.EIGHT) {
                throw new Error("Use an 8-bit RGB input copy.");
            }
            if (doc.colorProfileType === ColorProfile.NONE) {
                throw new Error("Assign the correct source profile to a copy first.");
            }
            doc.convertProfile("sRGB IEC61966-2.1", Intent.RELATIVECOLORIMETRIC, true, false);
            if (targets[i].exists) throw new Error("Output appeared before saving.");
            doc.saveAs(targets[i], opts, true, Extension.LOWERCASE);
            saved++;
        } catch (e) {
            failed.push(files[i].name + ": " + e.message);
        } finally {
            if (doc) {
                try { doc.close(SaveOptions.DONOTSAVECHANGES); }
                catch (e2) { closeErrors.push(files[i].name + ": " + e2.message); }
            }
        }
        // Stop if a document could not be closed; do not accumulate more open files.
        if (closeErrors.length) break;
    }
    alert("Saved: " + saved + " / " + files.length +
        "\nFailed: " + failed.length + "\n" + failed.join("\n") +
        "\nClose errors: " + closeErrors.length + "\n" + closeErrors.join("\n"));
}());