This snippet will return user defined properties on the window object.
This is useful for seeing what globals are being exposed to the window.
It works by creating an iframe and comparing the window element of the empty iframe.
function getWindowVars() {
// create an iframe and append to body to load a clean window object
const iframe = document.createElement('iframe')
// hide iframe
iframe.style.display = 'none'
// add iframe to page
document.body.appendChild(iframe)
// get the current list of properties on window
const currentWindow = Object.getOwnPropertyNames(window)
// filter the list against the properties that exist in the clean window
const results = currentWindow.filter(function(prop) {
return !iframe.contentWindow.hasOwnProperty(prop);
})
// Clean up iframe
document.body.removeChild(iframe)
return results
}
// usage:
const userDefinedVars = getWindowVars()
console.log(userDefinedVars)For example you might want to see if browser extensions are polluting the global window or what analytics tools a site has installed.