json - Jquery and getJson, only works when using alert() -

i having trouble jquery. seems acting oddly. what's going on. trying obtain equation json file , evaluating knockout observable objects.

what's weird it, works when use alert('') message, without it, doesn't work.

i googled question , answers regard ajax call. im using jquery function $getjson here

code

 function loaddata(filename) {       var data = $.getjson( filename + ".json");      return(data);  }       var res = 0;       var student = function(data) {      var self = this;      ko.mapping.fromjs(data, { }, self);       var res = 0;      self.result = ko.computed(function() {         loaddata("eqn").done(function(data1) {              if (data1 && data1.eqn) {                 $.each(data1.eqn, function(key, value){                     var str = value.equation;                     res = eval (str);                 });              }         });         return(res);          });      };  

everything working fine if add alert before return().

eqn.json

{    "eqn":[       {          "equation":"parsefloat(self.english()) + parsefloat(self.japanese()) + parsefloat(self.calculus()) + parsefloat(self.geometry())"       }    ] } 

data.json

{    "info":[       {          "name":"noob here",          "major":"language",          "sex":"male",          "english":"15",          "japanese":"5",          "calculus":"0",          "geometry":"20"       },       {          "name":"noob here",          "major":"calculus",          "sex":"female",          "english":"0.5",          "japanese":"40",          "calculus":"20",          "geometry":"05"       }    ] } 

complete code in here

edit

so main problem was, dependencies fetched json data. following workaround proved solution:

self.eqn = ko.observable(null);  self.reslut = ko.computed(function(){ return self.eqn() && eval( self.eqn() ); }); loaddata("eqn").done(function(data1) {    if (data1 && data1.eqn) {      $.each(data1.eqn, function(key, value){        self.eqn( value.equation;);      });   } }); 

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you cannot return asynchronous function. need set helper observable, value change in callback getjson.

right dont see why computed cant observable.

// let self.result simple observable self.result = ko.observable(); // call function update self.result loaddata("eqn").done(function(data1) {      if (data1 && data1.eqn) {         $.each(data1.eqn, function(key, value){             var str = value.equation;             res = eval (str);             // set value of self.result result of              // computing function             self.result( res );         });      } }) 

you need use ko.computed if variable depends on ko.observable

var = ko.observable("peter"),     b = ko.computed(function(){ return "hi " + (); }); 

in case, whenever update a, b updated. can see short hand following

var = ko.observable("peter"),     b = ko.observable("hi peter"); a.subscribe(function(v){ b( "hi " + v ); });