array adding function in object literal notation

Question

Here is the code I am using, not quite sure how to use literal notation yet, I have to pass the currentActiveCategories to the function somehow. Not sure if this is even the preferred way to do it, dont want to learn bad habits.

var primaryCare = {
    currentActiveCategories : [ "1", "2"],
    currentValue : addValues(this.currentActiveCategories)
}

function addValues(activeCategories) {
    tempTotal;
    for(int i = 0; i < activeCategories.length; i++){
        tempTotal += activeCategories[i];
    }
    return tempTotal;
}

What are you trying to achieve here? Are you trying to get a total of the items in the array just once at the time the object is created, or do you want to later be able to say primaryCare.currentValue() to get a current total at any time? (Also, are the array values supposed to be numbers or strings? Currently they're strings so your function will do string concatenation so the total will be "12".) — nnnnnn
– nnnnnn, Commented May 14, 2013 at 21:26

nnnnnn · Accepted Answer · 2013-05-14 21:34:21Z

2

Currently your object literal creates an object with two properties, currentActiveCategories, which is an array, and currentValue, which is set to the result of calling addValues() at the time the object literal is evaluated. You are trying to call the function with this.currentActiveCategories, which will be undefined, because this is not equal to that object at that moment.

If the idea is to have a function that can return the current total at any time you can do this:

var primaryCare = {
    currentActiveCategories : [ "1", "2"],
    currentValue : function () {
                      var tempTotal = "";
                      for(var i = 0; i < this.currentActiveCategories.length; i++){
                         tempTotal += this.currentActiveCategories[i];
                      }
                      return tempTotal;
                   }
}

primaryCare.currentValue(); // returns "12", i.e., "1" + "2"

Always declare your variables with var or they'll become globals - note that you can't declare an int in JS. You need to initialise tempTotal to an empty string before you start adding strings to it, or instead of "12" you'll get "undefined12".

When you call a function as a method of an object, like primaryCare.currentValue() (as shown above) then within the function this will be set to that object.

It seems kind of odd to me to be adding the values as strings. If you want to use numbers and get a numeric total you can do this:

var primaryCare = {
    currentActiveCategories : [ 1, 2],   // note no quotes around the numbers
    currentValue : function () {
                      var tempTotal = 0;
                      for(var i = 0; i < this.currentActiveCategories.length; i++){
                         tempTotal += this.currentActiveCategories[i];
                      }
                      return tempTotal;
                   }
}

answered May 14, 2013 at 21:34

nnnnnn

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3 Comments

Ian Over a year ago

Why are you giving the currentValue function a name?

Ian Over a year ago

And the original code wouldn't have worked because currentValue : addValues(this.currentActiveCategories) would've referred to window.currentActiveCategories

nnnnnn Over a year ago

@Ian - The function had a name due to copy/paste. Fixed. And I did say that this would not be that object, but it may or may not be window depending on whether all of that code is nested inside some other function.

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