The first tip for making your page's initial rendering faster is to gather all the required JavaScript files and place their <script> tags near the end of the page, preferably just before the closing </body> tag. This change will have a great impact on the time needed for the initial rendering of the page, especially for users with low speed connections such as mobile users. If you are already using the $(document).ready() method for all initialization purposes that relate to the DOM, moving the <script> tags around should not affect the functionality of your implementation at all.
The main reason for this is that, even though browsers download the page's HTML and other resources (CSS, images, and so on) in parallel, when a <script> tag is encountered, the browser pauses everything else until it is downloaded and executed. In order to work around this limitation of the specification, attributes like defer and async from HTLM5...