JavaScript function that can center a window opened with window.open

window-open.js

var openWindow = function (url, name, width, height, options) {
    "use strict";
    
    var finalOptions, opts, winTop, winLeft, finalTop, finalLeft, winHeight, winWidth;
    
    finalOptions = [];
    
    if (!options) {
        options = "";
    }
    
    // Make sure width is a number, else default to 400
    width = +width;
    if (isNaN(width)) {
        width = 400;
    }
    
    // Make sure height is a number, else default to 400
    height = +height;
    if (isNaN(height)) {
        height = 400;
    }
    
    if (options.indexOf("top=") < 0) {
        // If options doesn't contain "top" spec, define it
        winTop = +(window.screenY || window.screenTop || 50);
        winHeight = +(window.outerHeight || window.innerHeight || 500);
        finalTop = (winTop + ((winHeight / 2) - (height / 2)));
        finalOptions.push("top=" + finalTop);
    }
    
    if (options.indexOf("left=") < 0) {
        // If options doesn't contain "left" spec, define it
        winLeft = +(window.screenX || window.screenLeft || 50);
        winWidth = +(window.outerWidth || window.innerWidth || 500);
        finalLeft = (winLeft + ((winWidth / 2) - (width / 2)));
        finalOptions.push("left=" + finalLeft);
    }
    
    finalOptions.push("height=" + height);
    finalOptions.push("width=" + width);
    
    opts = finalOptions.join(",") + (options ? "," + options : "");
    
    return window.open(url, name, opts);
}