Resize Photoshop image to specified resolution

PS_resize_to_fit.js

// These are values for the end result width and height (in pixels) of our image
//
// Common values:
// Vk.com max photo size: 2560 x 2160

var target_width = 1920;
var target_height = 1080;

// ========================================================================================

#target photoshop
app.preferences.rulerUnits = Units.PIXELS;

var doc = app.activeDocument,
    cur_width = doc.width,
    cur_height = doc.height;

// Test height resize
var height_resize_new_height = target_height;
var height_resize_new_width = Math.round(cur_width * height_resize_new_height / cur_height);


// Test width resize
var width_resize_new_width = target_width;
var width_resize_new_height = Math.round(cur_height * width_resize_new_width / cur_width);


if (height_resize_new_width >= target_width) {
    doc.resizeImage(null, UnitValue(target_height, "px"), null, ResampleMethod.AUTOMATIC);
} else {
    doc.resizeImage(UnitValue(target_width, "px"), null, null, ResampleMethod.AUTOMATIC);
}

doc.resizeCanvas(UnitValue(target_width, "px"), UnitValue(target_height, "px"));