A guide to efficiently fetch JSON data synchronously using AngularJS

Trying to fetch data from a JSON file using AngularJS results in an error due to the asynchronous nature of the call. The code moves on to the next step before receiving the data, causing issues. The $http.get method was used.

$http.get('job.json').success(function (response) {
  $scope.big = response;      
});

Any suggestions for a synchronous method to retrieve JSON data?

{
  "days": [{
    "dayname": "Sun,23 Aug 2015",
    "date": "2015-08-23",
    "hours": "hoursArray(array24)"
  }, {
    "dayname": "Mon,24 Aug 2015",
    "date": "2015-08-24",
     "hours": "hoursArray(array24)"
  }, {
    "dayname": "Tue,25 Aug 2015",
    "date": "2015-08-25",
    "hours":"hoursArray(array24)"
  }, {
    "dayname": "Wed,26 Aug 2015",
    "date": "2015-08-26",
    "hours": "hoursArray(array24)"
  }]
}

The jQuery file currently being utilized:

(function($) {
$.fn.schedule = function(options) {
var methods = {
init : function(ele, opt) {
//methods.currentdate = methods.now.getFullYear() + "Engine Change" + methods.now.getMonth() + "Engine Change" + methods.now.getDate();
methods.currentdate = methods.now.getFullYear() + "-" + methods.now.getMonth() + "-" + methods.now.getDate();
// $("#scheduleAllDays > *").each(function(){
// var item = $(this);
// $("#scheduleAllDays").width($("#scheduleAllDays").width()+item.width());
// });
// $("#scheduleAllDays").width($("#scheduleAllDays").width());
ele.find("[data-row]").each(function() {
var drow = $(this), drowset = $("[data-row='" + drow.data("row") + "']");

var maxheight = methods.elesMaxHeight(drowset);
drowset.height(maxheight);
});
methods.allocateDurations(ele);
$("#scheduleContentInner", ele).css("min-height", $(".schedule-drag-wrap", ele).innerHeight());
},
elesMaxHeight : function(ele) {
var heights = $(ele).map(function() {
return $(this).height();
}).get();
return Math.max.apply(null, heights);
},
allocateDurations : function(ele) {
methods.flightdata = {
routes : {}
};
ele.find("[data-flight-row]").each(function(i, ival) {
var flight = $(this);
methods.flightdata.routes["row" + i] = [];
flight.find("[data-flight-record]").each(function() {
var currentFlight = $(this), flightrecord = methods.makeStringToObject(currentFlight.data("flight-record"));
flightrecord.element = currentFlight;
methods.flightdata.routes["row" + i].push(flightrecord);
});
});
methods.positionSet(ele);
},
positionSet : function(ele) {
var dayelement = $("#scheduleAllDays > *", ele);

var totaldaywidth = $("#scheduleAllDays").width() + 30;

var totaldays = dayelement.size();

var totalSeconds = (((totaldays * 24) * 60) * 60);
var perSecondsWidth = Number(totaldaywidth / totalSeconds);
var divider = $(".schedule-h-divider");
dayelement.each(function(i, ival) {
var dayele = $(this), dividerele = divider.eq(i);
dividerele.css({
top : $("#scheduleAllDays").height(),
left : dayele.offset().left - 104
});
});
for (var i in methods.flightdata.routes) {
var iobj = methods.flightdata.routes[i];
for (var j in iobj) {
var jobj = iobj[j];
var duration = jobj.duration, width = Number(methods.hmtosec(duration, ".") * perSecondsWidth);
var parent = jobj.element.parent();
jobj.element.css({
// position : "relative",
width : width + "px",
overflow : "hidden",
"white-space" : "nowrap"
}).parent().css({
// width : width+"px",
// overflow : "hidden"
// position:"absolute",
left : (j==0)?0:parent.prev().position().left+parent.prev().width()
});
}
}
methods.dragInit(ele);
},
setCurrentTimeMarker : function(ele) {
var marker = $(".schedule-current-time-marker");
var markerpills = $(".schedule-time-marker-pills");
var dayelement = $("#scheduleAllDays > *", ele);
var totaldaywidth = $("#scheduleAllDays").width() + 30;
var totaldays = dayelement.size();
var totalSeconds = (((totaldays * 24) * 60) * 60);
var perSecondsWidth = Number(totaldaywidth / totalSeconds);
var currentdate = new Date();
var format = currentdate.getFullYear() + "Engine Change" + currentdate.getMonth() + "Engine Change" + currentdate.getDate();
var currentdateele = $("#scheduleAllDays").find("[data-date='" + format + "']");
var days = (currentdateele.index()), seconds = ((days * 24) * 60) * 60;
seconds = seconds + methods.hmtosec(currentdate.getHours() + "." + currentdate.getMinutes(), ".");
marker.stop().animate({
top : $("#scheduleAllDays",ele).height()-53,
left : (seconds * perSecondsWidth) - (marker.width() / 2)
}, 1000, "swing");
markerpills.html(currentdate.getHours() + ":" + currentdate.getMinutes());
methods.markermove = setInterval(function() {
currentdate = new Date();
marker.css({
left : marker.position().left + perSecondsWidth
}, "fast", "swing");
markerpills.html(methods.makezerodigit(currentdate.getHours()) + " : " + methods.makezerodigit(currentdate.getMinutes()));
// methods.schedulemove(ele,perSecondsWidth);
}, 1000);
},
schedulemove : function(ele,seconds) {
var dragwrap = ele.find(".schedule-drag-wrap");
var routewidth = $(".schedule-route:eq(0)").width() + $(".schedule-route:eq(1)").width();
var maxleft = -(dragwrap.width() - ($(window).width() - routewidth));
if (Math.abs(dragwrap.position().left) < Math.abs(maxleft)) {
dragwrap.css({
left : (dragwrap.position().left - (dragwrap.width)) + "px"
});
}
},
makezerodigit : function(digit) {
return (String(digit).match(/^[0-9]$/)) ? "0" + digit : digit;
},
dragInit : function(ele) {
var currentdaycol = $("[data-date='" + methods.currentdate + "']");
ele.find(".schedule-drag-wrap").css({
left : -(currentdaycol.position().left - 50) + "px"
}).animate({
left : -currentdaycol.position().left - 0 + "px"
}, 1000, "swing", function() {
methods.drag(ele);
methods.setCurrentTimeMarker(ele);
});
},
drag : function(ele) {
methods.move = null;
$(".schedule-drag-wrap", ele).on("mousedown", function(e) {
var dragele = $(this), position = dragele.position();
methods.move = {
x : e.pageX,
y : e.pageY,
left : position.left
};
}).on("mouseup mouseleave", function(e) {
var dragele = $(this);
if (methods.move) {
methods.move = null;
dragele.removeClass("userselect-none cursor-move");
}
}).on("mousemove", function(e) {
var dragele = $(this), position = dragele.position(), movedx, drag = true;
if (methods.move) {
methods.curmove = {
x : e.pageX,
y : e.pageY
};
var routewidth = $(".schedule-route:eq(0)").width() + $(".schedule-route:eq(1)").width();
var maxleft = -(dragele.width() - ($(window).width() - routewidth));
var xcondition = (methods.move.x > methods.curmove.x);
dragele.addClass("userselect-none cursor-move");
if (position.left <= maxleft && xcondition) {
drag = false;
dragele.css({
left : maxleft
});
}
if (position.left > -10 && !xcondition) {
drag = false;
dragele.css({
left : 0
});
}
if (drag) {
//if direction right to left
movedx = methods.move.left + (methods.curmove.x - methods.move.x);
dragele.css({
left : movedx
});
}
}
});
},
now : new Date(),
currentdate : "",
hmtosec : function(hours, identy) {
var s = (hours.match(/\./)) ? hours.split(identy) : [hours, 0], h = s[0], m = s[1];
h = (Number(h)) ? (h * 60) * 60 : 0;
m = (m == 0) ? 0 : m * 60;

return Number(h + m);

},
makeStringToObject : function(string) {
var loc_string = String(string).split("|");
var output = {};
for (var i in loc_string) {
var keyvalue = loc_string[i].split("~");
output[keyvalue[0]] = keyvalue[1];
}
return output;
}
};
return this.each(function() {
methods.init($(this), $.extend({}, $.fn.schedule.setting, options));
});
};
$.fn.schedule.setting = {};
})(jQuery);
The encountered error: Uncaught TypeError: Cannot read property 'left' of undefined

javascriptjsonangularjs

Answer №1

When utilizing a service: 

var deferred = $q.defer();
       $http.get('job.json')
    .success(function(response) {
     defer.resolve(response);
    }).error(function(error){
    console.log(error);
    })
        return deferred.promise;

In the controller section:

var p=<serviceCall>
p.then(function(s){
$scope.ans=s;
})

The $q serves the purpose of obtaining synchronous responses. For further information please visit:https://docs.angularjs.org/api/ng/service/$q

Answer №2

Performing a synchronous HTTP request is not possible because the response (which in this case is the JSON file) cannot be instantly loaded. However, when using $http.get, it returns a promise that resolves once the request is complete. To handle actions after the JSON file has been loaded, you should execute them within the then block of the promise.

$http.get('data.json').then(function (response) {
  $scope.data = response;
  // Carry out any additional tasks after loading the JSON file.
});

Answer №3

To update your value, use promise.then in the following code snippet:

    var promise=$http.get('data.json');
    promise.then(function(data){
                  $scope.value=data;
    });

An alternative approach is shown below:

   function fetchObj(callback){
    $http.get('data.json').success(callback);
   } 

  fetchObj(function(output){
   console.log(output)
   // include your jQuery script here
  })

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