I am trying to use twig json_encode function but when I do this
var packageDetails = {{(packageDetails|json_encode)}};
and packageDeta
Is it simply because you are not wrapping your output in quotes?
var variable = '{{{reference}}}';
Update:
The actual answer to solve the question was adding |raw to the tag as per comments
var packageDetails = {{(packageDetails|json_encode|raw)}};
You can add the options in the following way:
{{ data|json_encode(constant('JSON_PRETTY_PRINT'))|raw }}
Adding this because it answers the question in your title, but it sounds like the raw filter was really what you were looking for. Still, others may find this useful.
For anyone, who has similar problem with Blade / Laravel5.x
var v = JSON.parse('{!! $v !!}');