Conditional resize image script for Photoshop. No save, only resize to desired area.

imageResize.jsx

var image = app.activeDocument;
var imageRatio = image.width / image.height;

// change this to true if you want to upscale if the image is smaller than the desired area
var upscale = false;

var area = {
      width: 700,
      height: 500
};

area.ratio = area.width / area.height;

var scale;

if(imageRatio >= area.ratio){
      scale = area.width / image.width.value;
} else {
      scale = area.height / image.height.value;
}

if (upscale) {
      image.resizeImage(UnitValue(image.width * scale,"px"),UnitValue(image.height * scale,"px"),null,ResampleMethod.AUTOMATIC);
} else if(scaleThumb < 1){
      image.resizeImage(UnitValue(image.width * scale,"px"),UnitValue(image.height * scale,"px"),null,ResampleMethod.AUTOMATIC);
}

Check this GIST for 2 resize versions and JPG saving
https://gist.github.com/PierBover/2ce931fd092c5cba99dc

There is no scaleThumb, I am guessing you meant scale on line 24, also you can just combine the conditional to if (upscale or scale < 1)