JavaScript module shared between node or browser

portable_js.js

(function(exports){
    
    // Only allow files uploaded below a maximum size
   exports.isValidSize = function(sourceSize){
        var maxSize = 1024 * 1024 * 10; // 10MB
        
        return sourceSize <= maxSize;
    };

})(typeof exports === 'undefined'? this['lib.image']={}: exports);

// -----------------------------------------------------------------

// Use in Node.JS
var imageHelper = require('lib.image');
imageHelper.isValidSize(1024); // true

// Use client side
// <script src="localhost:3000/lib.image.js"></script>
<script>
    var isValidSize = lib.image.isValidSize(1024); // true
</script>