When I first started writing client-side applications, the process was terrible. I had to save my file and then flip over to my browser to check my results. As a result, I was clicking two buttons every time I wanted to save a file. To make matters worse, I had to repeat the process to test my application in multiple browsers. To test a minimum of Chrome, Firefox and a single version of Internet Explorer, I was clicking 4 buttons. To repeat that flow over and over again to test incremental changes was soul killing.