List all js global variables used by site (not all defined!)

Solution 1:

In Chrome, go to Dev tools and open the console. Then type in the following:

Object.keys( window );

This will give you an Array of all the global variables.

EDIT

After searching on Google a bit, I found a way. You will need firefox and the jslinter addon.

Once setup, open jslinter and go to Options->check everything on the left column except "tolerate unused parameters".

Then run jslinter on the webpage and scroll down in the results. You will have a list of unused variables (global and then local to each function).

Now run Object.keys(window); in the console and compare the results from both to figure out which ones are used.

Solution 2:

This one-liner will get you pretty close, and does not require installing anything additional, or running code before the page loads:

Object.keys(window).filter(x => typeof(window[x]) !== 'function' &&
  Object.entries(
    Object.getOwnPropertyDescriptor(window, x)).filter(e =>
      ['value', 'writable', 'enumerable', 'configurable'].includes(e[0]) && e[1]
    ).length === 4)

It filters Object.keys(window) based on three principles:

Things that are null or undefined are usually not interesting to look at.
Most scripts will define a bunch of event handlers (i.e. functions) but they are also usually not interesting to dump out.
Properties on window that are set by the browser itself, are usually defined in a special way, and their property descriptors reflect that. Globals defined with the assignment operator (i.e. window.foo = 'bar') have a specific-looking property descriptor, and we can leverage that. Note, if the script defines properties using Object.defineProperty with a different descriptor, we'll miss them, but this is very rare in practice.

Solution 3:

What i did was. I found a page with as little JavaScript / Frameworks as possible, logged all their keys in array. Then iterated all the keys on the new page and logged only those which were not listed in the previous site. You can try it or use my code snippet

var ks = ["postMessage","blur","focus","close","frames","self","window","parent","opener","top","length","closed","location","document","origin","name","history","locationbar","menubar","personalbar","scrollbars","statusbar","toolbar","status","frameElement","navigator","customElements","external","screen","innerWidth","innerHeight","scrollX","pageXOffset","scrollY","pageYOffset","screenX","screenY","outerWidth","outerHeight","devicePixelRatio","clientInformation","screenLeft","screenTop","defaultStatus","defaultstatus","styleMedia","onanimationend","onanimationiteration","onanimationstart","onsearch","ontransitionend","onwebkitanimationend","onwebkitanimationiteration","onwebkitanimationstart","onwebkittransitionend","isSecureContext","onabort","onblur","oncancel","oncanplay","oncanplaythrough","onchange","onclick","onclose","oncontextmenu","oncuechange","ondblclick","ondrag","ondragend","ondragenter","ondragleave","ondragover","ondragstart","ondrop","ondurationchange","onemptied","onended","onerror","onfocus","oninput","oninvalid","onkeydown","onkeypress","onkeyup","onload","onloadeddata","onloadedmetadata","onloadstart","onmousedown","onmouseenter","onmouseleave","onmousemove","onmouseout","onmouseover","onmouseup","onmousewheel","onpause","onplay","onplaying","onprogress","onratechange","onreset","onresize","onscroll","onseeked","onseeking","onselect","onstalled","onsubmit","onsuspend","ontimeupdate","ontoggle","onvolumechange","onwaiting","onwheel","onauxclick","ongotpointercapture","onlostpointercapture","onpointerdown","onpointermove","onpointerup","onpointercancel","onpointerover","onpointerout","onpointerenter","onpointerleave","onafterprint","onbeforeprint","onbeforeunload","onhashchange","onlanguagechange","onmessage","onmessageerror","onoffline","ononline","onpagehide","onpageshow","onpopstate","onrejectionhandled","onstorage","onunhandledrejection","onunload","performance","stop","open","alert","confirm","prompt","print","requestAnimationFrame","cancelAnimationFrame","requestIdleCallback","cancelIdleCallback","captureEvents","releaseEvents","getComputedStyle","matchMedia","moveTo","moveBy","resizeTo","resizeBy","getSelection","find","webkitRequestAnimationFrame","webkitCancelAnimationFrame","fetch","btoa","atob","setTimeout","clearTimeout","setInterval","clearInterval","createImageBitmap","scroll","scrollTo","scrollBy","onappinstalled","onbeforeinstallprompt","crypto","ondevicemotion","ondeviceorientation","ondeviceorientationabsolute","indexedDB","webkitStorageInfo","sessionStorage","localStorage","chrome","visualViewport","speechSynthesis","webkitRequestFileSystem","webkitResolveLocalFileSystemURL","addEventListener", "removeEventListener", "openDatabase", "dispatchEvent"]
var newKs = []
for (key in window) {
    if(ks.indexOf(key) == -1 && key !== "ks" && key !=="newKs") {
        newKs.push(key);
    }
}
console.log(newKs);

Solution 4:

You could try to use getters for that, which you create for all existing global variables. Run this before the page is started:

Object.keys(window) // or
Object.getOwnPropertyNames(window).concat(
  Object.getOwnPropertyNames(Object.getPrototypeOf(window))
) // or whatever
.forEach(function(name) {
    var d = Object.getOwnPropertyDescriptor(window, name),
        def = Object.defineProperty,
        log = console.log.bind(console);
    if (d && !d.configurable)
        return log("cannot detect accessing of "+name);
    def(window, name, {
        configurable: true,
        get: function() {
            log("window."+name+" was used by this page!");
            if (d) {
                def(window, name, d);
                return d.get ? d.get() : d.value;
            } else { // it was not an own property
                delete window[name];
                return window[name];
            }
        },
        set: function(x) {
            log("Ugh, they're overwriting window."+name+"! Something's gonna crash.");
        }
    });
});

Of course property descriptors etc. are not compatible with older browsers. And notice that there are some global variables / window properties that might not be programmatically listable (like on* handlers), if you need them you will have to explicitly list them in the array. See the related questions List all properties of window object? and Cross Browser Valid JavaScript Names for that.

Yet I guess running a code coverage tool that whinges about undeclared global variables, like @stackErro suggested, is more helpful.

Solution 5:

Since this question is the first in google when searching for a way how to list global javascript variables, I will add my own answer for that. Sometimes you need to list global variables to see if your code does not have a variable leaked outside the scope (defined without 'var'). For that, use this in the debug console:

(function ()
{
   var keys=Object.keys( window );
   for (var i in keys)
   {
      if (typeof window[keys[i]] != 'function')
      console.log(keys[i], window[keys[i]]);
   }
})();

It will list the standard global variables, like window, document, location, etc. Those are just few. So you can find your leaked vars in the list easily.