javascript - JQuery: parameter: hard-coded string vs ajax retrieved string -

i trying jquery token input prepopulated.

var assignuserjson=$('#assignuserjson').val(); console.log(assignuserjson); //[{"id":"1","name":"andrew"},{"id":"3","name":"john"}] 

here difference between 2 ways supposed should work in:

$('#assigntask').tokeninput('/users/suggest', {prepopulate: assignuserjson}); // doesn't work   

and works:

$('#assigntask').tokeninput('/users/suggest', {prepopulate: [{"id":"1","name":"andrew"},{"id":"3","name":"john"}]}); // works   

why that? shouldn't able value hidden input field , pass tokeninput function?

in first method, assignuserjson string whereas in second method, array object. objectifying first 1 should work:

$('#assigntask').tokeninput('/users/suggest', {prepopulate: json.parse(assignuserjson)});