Thanks a lot @thomasneirynck.
I am not able to use resize_checker lib and it returns me a function as -
var ResizeChecker = Private(require('ui/vislib/lib/resize_checker'));
console.log(ResizeChecker) prints me a function which contains verious functions.
I am bit new to javascripting , so how do invoke function like read() from this ResizeChecker instance?
I tried
console.log(ResizeChecker.prototype.read());
which returns TypeError: Cannot read property '0' of undefined