Javascript object prototype function

Question

I have three methods in an object.

2 of them work properly, when third is printed - it prints out the code itself, not function. Here is the code and how it looks in console:

function Students(name, lastname, grades){
    this.name = name;
    this.lastname = lastname;
    this.grades = grades;
    this.addGrade = function(a){
        this.grades.push(a);
    }
    this.printData = function(){
        console.log("Name: " + this.name);
        console.log("Grades: " + this.grades);
        console.log("Average: " + this.gradeAvg);
    }
    this.gradeAvg = function(){
        console.log("blabla");
    }
}

var StudentasA = new Students("Petras", "Petrauskas", [8, 9, 9, 8, 7]);
var StudentasB = new Students("Jurgis", "Jurgauskas", [6, 7, 5, 4, 9]);
StudentasA.printData();
StudentasA.addGrade(28);
StudentasA.printData();

console:

console view

You aren't actually using a prototype.

SLaks
– SLaks

2016-12-13 21:34:35 +00:00
Commented Dec 13, 2016 at 21:34 — SLaks
– SLaks, Commented Dec 13, 2016 at 21:34

Nina Scholz · Accepted Answer · 2016-12-13 21:36:29Z

1

You need to call the function

this.gradeAvg()
//           ^^

function Students(name, lastname, grades){
    this.name = name;
    this.lastname = lastname;
    this.grades = grades;
    this.addGrade = function(a){
        this.grades.push(a);
    }
    this.printData = function(){
        console.log("Name: " + this.name);
        console.log("Grades: " + this.grades);
        console.log("Average: " + this.gradeAvg());
        //                                     ^^
    }
    this.gradeAvg = function(){
        return this.grades.reduce(function (a, b) { return a + b; }) / this.grades.length;
    }
}

var StudentasA = new Students("Petras", "Petrauskas", [8, 9, 9, 8, 7]);
var StudentasB = new Students("Jurgis", "Jurgauskas", [6, 7, 5, 4, 9]);
StudentasA.printData();
StudentasA.addGrade(28);
StudentasA.printData();

answered Dec 13, 2016 at 21:36

Nina Scholz

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Comments

SLaks · Accepted Answer · 2016-12-13 21:35:06Z

1

Your code never actually calls the function.

Instead, you concatenate the function itself directly into the string.

You want parentheses.

answered Dec 13, 2016 at 21:35

SLaks

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