The arr.length is still undefined after I call _.chain() underscore operation:
var arr = _.chain(msg)
.groupBy(function(item) {return item.ts_simple; })
.value();
console.log(arr.length); //undefined
console.log(arr); //correct object array
The first console.log(arr.length) for underscore var array length is undefined while the console.log(arr) outputs the correct returned object array.
How do I callback after underscore operation is complete?