How to read URL parameters from Unity WebGL Build

I am building a browser based game targeting WebGL platform. Once I build my game into WebGL, I am getting an index.html file and gamename.js file (Ignoring other generated files as I assume they might be relevant here). > Once I host the file, I will need to read the URL parameters which will be passed while I call the URL of my game. The parameter can be something like an API key for instance, which will be used to connect the game to my back-end system. > So I need to know how can I access and use those parameters inside my game. Any information on the same is welcomed. Thanks in advance