javascript - How does asynchronous call work in AngularJS 1.X? $Http call not returning value -

i have following function named getvalue. inside angularjs module controller. trying call function on click event invoking function in controller.(i hope clear)

function:

  function getvalue(data, $http) {             var value=undefined;            $http({                 url: /myurl,                 method: "get",                 params: {                     tmp: data.tmp,                     pressure: data.pressure                                }             }).success(function (data, status, headers, config) {                             value=parsefloat(  console.log(data));//console working here                return value;             });         return value;         } 

code inside controller

 value= getvalue(formdata, $http );         alert(value);//undefined here. seems value never changed. 

i have not getting value on alert console printing value. need if possible 2 issues.

1. how can change value inside success , return controller?
2. is there way don't have inject $http controller function? -----it nice if can unit testing.

you ideally want pull $http service out of controller , make factory calls.

in factory have function accepts data wanting send , have return promise controller

something this

repo

app.factory("foorepo", ["$http", function($http){     return {         getvalue: function(data){             return $http({                 method: "post",                 url: "/myurl"             });         }     }; }]); 

serivce

app.factory("foo", ["$q", "foorepo", function($q, foorepo){     return {         getvalue: function(data){             var deferred = $q.defer();              foorepo.getvalue(data)             .success(function(results){                 //do work                 deferred.resolve(results);             })             .error(function(error){                 // work                 deferred.reject(error);             });              return deferred.promise;         }     } }]); 

here controller

app.controller("fooctrl", ["foo", function(foo){     foo.getvalue(datahere)         .then(function(results){             // here         }); }]); 

added plunkr