4. Odd .sort function behavior

Odd .sort function behavior


  • I am writing a .sort function that sorts an array of objects by one of their properties. See the snippet below. 

    PriorityQueue.prototype.sort = function () {
     var criterium = this.criteria; // For some reason using this.criteria in the next line doesn't work.
     this.queue.sort(function(a,b) {
     return b[criterium] - a[criterium]
     });
    }

    This works, but I'm curious why I have to define the variable criterium. If I were to use this.criteria within the sort function (i.e. "return b[this.criteria] - a[this.criteria]) then they return 'undefined'. For example, see the below code 

    PriorityQueue.prototype.sort = function () {
     var criterium = this.criteria;
     this.queue.sort(function(a,b) {
     return console.log(a[criterium] + '___' + a[this.criteria]) // 10___undefined 
     });
    }

    Here, a[criterium] correctly returns its associated number (10) whereas a[this.criteria] returns undefined. This happens despite that criterium = this.criteria. 

    Does anyone know why I can't use this.criteria within the sort function? 

     

  • Culture

    Check this article http://stackoverflow.com/questions/8670877/this-value-in-javascript-anonymous-function