Check if Javascript script exists on page

Question

I have a bookmarklet that I\'ve made and it loads a script from my server onto the users current page. However I have an if check in my script that if a condition is not met the

Answer 1

if you create a variable in the global scope (window.yourVariable) and check if that exists already then you can decide if you want to add your jsCode snippet code or run whatever you are running in script.js