Tern & Completion String support - angelozerr/tern.java GitHub Wiki

String completion plugin will gather (short) strings in your code, and completing when inside a string will try to complete to previously seen strings. Takes a single option, maxLength, which controls the maximum length of string values to gather, and defaults to 15.

To activate this mode, you must check the Guess Completion tern plugin. After installing and converting your project as Tern Project, go at Tern project property, click on Tern / Modules item and select the Completion String tern plugin :

After that you can benefit with string completion :