javascript - scope of `this` changing on a production server? -

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i have following 3 functions in backbone view. originally, call updatetimer within playback , startrecording functions triggered error, went away after preceded call this, in this.updatetimer. however, i've put demo app on production server (where code compiled 1 file) , call this.updatetimer triggering error

 uncaught typeerror: object #<object> has no method 'updatetimer' (repeated 28 times)

can explain why might be?

the 3 functions working on local machine:

     playback: function(e){          e.preventdefault();         this.updatetimer(0);         sc.recordplay({             progress: function(ms) {                 this.updatetimer(ms);             }         });        },        updatetimer: function(ms){          $('.status').text(sc.helper.millisecondstohms(ms));         },        startrecording: function(e){           $('#startrecording').hide();           $('#stoprecording').show();           e.preventdefault();           sc.record({             progress: function(ms, avgpeak) {               this.updatetimer(ms);             }           });        },

from console of production server

,playback: function(t) {         t.preventdefault(), this.updatetimer(0), sc.recordplay({progress: function(t) {                 this.updatetimer(t)             }})     },updatetimer: function(t) {         $(".status").text(sc.helper.millisecondstohms(t))     },startrecording: function(t) {         $("#startrecording").hide(), $("#stoprecording").show(), t.preventdefault(), sc.record({progress: function(t) {                 this.updatetimer(t) uncaught typeerror: object #<object> has no method 'updatetimer' (repeated 28 times)             }})

you getting error because this context lost in inner function passing sc.record , no longer refers backbone view. there few ways around this, 1 of take advantage of closures , create reference correct this , use in progress callback:

  startrecording: function(e){      var self = this;      $('#startrecording').hide();       $('#stoprecording').show();       e.preventdefault();       sc.record({         progress: function(ms, avgpeak) {           self.updatetimer(ms);         }       });    },

same thing goes call updatetimer in call sc.recordplay in playback.


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