javascript - Backbone Model array property change and change event listener not always firing -


this question has answer here:

i found strange in backbone using change events. it's model wich has array property. , if property push new value inside , set model change event not fired...

here's documented example:

var testmodel = backbone.model.extend({     defaults : {         numbers : []     },      initialize : function() {         this.on('change:numbers', this.changedevent);     },      changedevent : function() {         console.log('model has changed');     } });  var otestmodel = new testmodel();     otestmodel.set('numbers', [2, 3, 4]);    // change:numbers event fired  var anumbers = otestmodel.get('numbers');     anumbers.push(5);  otestmodel.set('numbers', anumbers);    // change:numbers event not fired why???  // otestmodel.set('numbers', [2, 3, 4]);  // if line not commented out change:numbers event fired  console.log(otestmodel.tojson());  // dumps out [2,3,4,5] respective [2,3,4] if line above not commented out

thx in advance.

hesson absolutely right about:

arrays in javascript treated pointers, mutating array not change pointer, , no "change" event fired.

however, alternate solution (if using underscore.js) can do:

var anumbers = _.clone(otestmodel.get('numbers')); anumbers.push(5);  otestmodel.set('numbers', anumbers); //will trigger changed:numbers event

as seen in answer similar problem: backbone.js : change not firing on model.change()

this duplicate object instead of making reference, nested objects or arrays references.


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