CODEWITHSUNDEEP
javascript
vicky
vicky

Reputation: 2149

Javascript produces undesirable output

I am basically from java background so I wrote a JavaScript code in which a variable act as private variable , Here is my code

var myObject = function(){
    var teamScore = 0;  
    return {
        playSix: function() {
            teamScore += 6
        },

        playFour: function() {
            teamScore = teamScore +4
        },

        getScore: function(){
            return teamScore;
        },

        getMScore : teamScore
    }
}();



 myObject.playSix();

alert ("What is the team score  :" + myObject.getScore())
alert ("What is the M-score  :" + myObject.getMScore)

Desired output is

What is the team score : 6 ; What is the M-score : 6

But the actual output is

What is the team score : 6 ; What is the M-score : 0

Why M-score is 0 ?

Upvotes: 0

Views: 58

Answers (6)

GoBusto
GoBusto

Reputation: 4778

When you define the object, you are setting teamScore = 0 and then getMScore : teamScore. In other words, the value of teamScore will be used to initialise getMScore.

Note that "value" is the key word here - this code is not assigning a reference to the teamScore variable, it's literally just copying the current value from one to the other. getMScore will not change if teamScore does, because the two values are independent.

Upvotes: 1

Praveen Tiwari
Praveen Tiwari

Reputation: 1310

If you look closely, getScore is a function which when called return the current value of teamScore. So, when you called myObject.playSix(); teamScore would become 6. Now calling getScore would return current value of teamScore = 6

On the other hand, getMScore gets assigned to initial value of teamScore (which is 0) and remains the same. Hope it makes sense.

Upvotes: 2

Alex Kopachov
Alex Kopachov

Reputation: 733

This happens because getScore is a function, and it will get actual result of teamScore all the time you call it. But getMScore is just simple static value which you have set before returning. Pay attention that getMScore is not some kind of "shortcut" or "pointer" to teamScore, it's just simple value.

To fix this you should write getMScore as function, for example:

getMScore : function() { return teamScore; }

and call it like this:

alert ("What is the M-score  :" + myObject.getMScore())

Upvotes: 3

void
void

Reputation: 36703

getMScore is initialized with 0

Because when you defining the object the teamScore is equal to 0 and getMScore : teamScore will also get a 0 doesnt matter you change it afterwards.

Upvotes: 2

Guffa
Guffa

Reputation: 700172

That's because the getMScore is initialised to zero, and never changes.

The property getMScore is not a reference to the teamScore variable, it's only initialised with the value of the teamScore variable at the time that the object is created. When the teamScore variable is changed, the getMScore property is unaffected.

Upvotes: 4

Naeem Shaikh
Naeem Shaikh

Reputation: 15715

The getMScore, your are referring to, in myObject , is already assigned to 0, when teamscore initially was 0,

So even if you change value for teamscore, it will still return the value which was returned prior to changing the value of teamscore

Upvotes: 2

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