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JavaScript Object-Oriented JavaScript (2015) Introduction to Methods Modifying Objects with Methods

Posted by john larson
john larson
16,594 Points

What am I missing, getting undefined...

//at this point we are running it in the console with...
//calculator.add(2) 
//calculator.add(5)
//calculator.equals()
//and I'm getting undefined

 var calculator = {
    sum: 0,
    add: function(value){
    this.sum += value; // update the value w/sum
  },
    clear: function(){
    this.sum = 0;
    },
    equals: function(){
    return this.sum
    }
}

4 Answers

Jennifer Nordell
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STAFF
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Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
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Jennifer Nordell
Treehouse Teacher

Well, you're missing one semicolon. But that's not affecting anything. Remember that while you're adding, nothing is being returned. The return doesn't happen until you call/invoke the equals method. This can also be seen as having undefined in the console at 2:53 in the video. It does this until Andrew calls the equals method when it then actually returns something.

Hope this helps! :sparkles:

john larson
john larson
16,594 Points

I thought I called it with calculator.equals(), but I'm still getting undefined at that point.

//I copied this out of the console


calculator.add(2)
undefined
calculator.add(2)
undefined
calculator.equals()
undefined
Jennifer Nordell
seal-mask
.a{fill-rule:evenodd;}techdegree
Jennifer Nordell
Treehouse Teacher
Jennifer Nordell
.a{fill-rule:evenodd;}techdegree
Jennifer Nordell
Treehouse Teacher

I have absolutely no idea! I'm running your code, in both Firefox and Chrome (even with the missing semicolon), and I'm getting back the result when I do calculator.equals(). What browser are you using?

This is from my console in Chrome:

 var calculator = {
    sum: 0,
    add: function(value){
    this.sum += value; // update the value w/sum
  },
    clear: function(){
    this.sum = 0;
    },
    equals: function(){
    return this.sum
    }
}
undefined
calculator.add(2)
undefined
calculator.add(3)
undefined
calculator.equals()
5
arajay
arajay
4,463 Points

calculator.equals() returns 'undefined' in firefox, but returns the correct value in chrome.

changing the return function from this.sum to caculator.sum; resolves the issue.

john larson
john larson
16,594 Points
john larson
john larson
16,594 Points

chrome, Thanks Jenifer...I'll just scrap my code and start over...again

Tom Emody
Tom Emody
1,808 Points
Tom Emody
Tom Emody
1,808 Points

I have this same problem. For some reason when I run this code as a preview through teamtreehouse, it gives me undefined when i do calculator.equals()

It also seems to not actually change the value of sum. However if I open up a console other than the preview one from treehouse, it works.

Joshua Elder
Joshua Elder
2,767 Points
Joshua Elder
Joshua Elder
2,767 Points

Have you made sure you are saving the calculator.js file and then reloading the dice simulator page?