A script to export images in photoshop with max with and file size

SaveforWebSP.jsx

//SaveforWebSP.jsx  
var docRef = activeDocument;
var outputFolder = docRef.path;

var segments = app.activeDocument.name.split(".");
segments.splice(segments.length - 1, 1);
var docName = segments.join(".");

var fileName = prompt("Please Enter a file name without extension?", docName);
var safeFileName = fileName.replace(/[^A-Z0-9]+/ig, "_");
var fileExt = prompt("Please Enter a file name without extension?", "jpg");

if (safeFileName.length > 0) {
    var NewfileRef = new File(outputFolder + "/" + safeFileName + "_aem." + fileExt);
    var w = 2000; // new file width  
    var MaxSz = 500000; // max. 500Kb  
    var Qlt = 100; // initial quality 100  
    var x = 10; // decreasing step  
    // resize the image to the right width  
    docRef.resizeImage(UnitValue(w, "px"), null, 100, ResampleMethod.BICUBICSHARPER);
    // Perform the first SaveForWeb Operation  
    ExpWeb(NewfileRef, Qlt);
    // Keep trying to save the file with max. Qlt, but under MaxSz      
    while (NewfileRef.length > MaxSz) {
        Qlt = Qlt - x;
        NewfileRef = new File(NewfileRef);
        NewfileRef.remove();
        ExpWeb(NewfileRef, Qlt); // Perform a new SaveForWeb Operation, with slightly lower Qlt  
        if (Qlt <= 0) {
            alert("The file can't be saved with the desired size AND quality.");
            break // break the loop whenever the quality is as low as 50 (this shouldn't need to happen)  
        }
    }
    var FileSz = NewfileRef.length / 1024;
    FileSz = Math.round(FileSz);
    // close the original file without saving  
    activeDocument.close(SaveOptions.DONOTSAVECHANGES);
} else {
    alert("Please try again with a file name");
}

// SaveForWeb Export, with the desired constraints and parameters  
function ExpWeb(FileNm, Qlt, type) {
    var options = new ExportOptionsSaveForWeb();
    options.quality = Qlt; // Start with highest quality (biggest file).  
    if (type = "png") {
        options.format = SaveDocumentType.PNG; // Save Format for the file  
    } else {
        options.format = SaveDocumentType.JPEG; // Save Format for the file 
    }
    docRef.exportDocument(File(FileNm), ExportType.SAVEFORWEB, options);
}