Existing implementations were designed `` for small programs , where the performance and interactivity of the system were n't that important '' but web applications like Gmail `` are using the web browser to the fullest when it comes to DOM manipulations and Javascript '' . According to Google , existing implementations were designed `` for small programs , where the performance and interactivity of the system were n't that important '' , but web applications such as Gmail `` are using the web browser to the fullest when it comes to DOM manipulations and JavaScript '' , and therefore would significantly benefit from a JavaScript engine that could work faster .