Add Custom JavaScript to SPO 2013

<!--1) Upload your js file in the root folder of your master page-->

<!--You can do it too in the style library-->

<!--2)Use the SharePoint Script tag to point the js code to your master page-->

<SharePoint:Scriptlink ID="Scriptlink9" runat="server" name="~SiteCollection/Style Library/YourFolderName/YourScriptName.js" language="javscript" />