Question

I currently create an object on page load with all possible key/value pairs and use true or false to determine their state. It would be more efficient if only items that were true were present though.

Sample data:

    filter =  {
            "country": 1,
            "Age Group": {
                2: false,
                3: true,
                4: false,
                5: false,
                6: false,
                7: false
            },
            "Gender": {
                1: false,
                2: false
            },
            "NEWSEC": {
                1: false,
                2: true,
                3: false,
                4: false,
                5: false
            },
            "Telco_Segment": {
                1: true,
                2: true,
                3: true,
                4: false,
                5: false,
                6: false
            }
    };

function:

function facetBuilder(key, val)
{
    if(key == 'country')
    {   
        filter.country = val;
    }
    else
    {
        if( filter[key][val] == true )
        {
            filter[key][val] = false;
        }
        else
        {
            filter[key][val] = true;
        }
    }
    console.log(filter);
}

Problem:

The function I use to apply these filters loops through them, so it would be more beneficial if I only had the objects such as “Age Group” present if it contained any values. In fact, it would be nice to have something like the following:

    filter =  {
            "country": 1,
            "Age Group": [3],
            "NEWSEC": [2],
            "Telco_Segment": [1,2,3]
    };

calling facetBuilder would essentially add/remove an object based on the presence of value(s) for that object.

I’m drawing a blank on how to approach this one.

Answer 1

You don’t need to explicitly check for true. You can check for the existence for an entry by doing something like this:

if(map[key]) {
  ...
  ...
}

However if the value associated with that key is 0, then this is a problem, so it’s better to do:

if(typeof map[key] !== "undefined") {
   ...
   ...
}

The reason you want to use typeof in this case is that a direct comparison against undefined can be problematic due to the possibility of undefined being overwritten by other code:

window.undefined = "not undefined";
"not undefined" == "undefined" //returns a true value

Then your code would look like this:

if(typeof filter[key][val] !== "undefined" )
{
    delete filter[key][val]; //I'm assuming you want to remove it
}
else
{
    filter[key][val] = true;
}

Another thing, when checking for a true value, it’s enough to say

if([expression that evaluates to a boolean value]) {
    ...
}

You don’t have to do:

if([expression that evaluates to a boolean value] == true) {
    ...
}

or

if([expression that evaluates to a boolean value] == false) {
    ...
}

Another way to check for the existence of a property is to use the in operator:

var stuff = {
   a: 10,
   c: 20,
   d: 30
};

var ay = "a"
console.log(ay in blab, "b" in blab, "c" in blab, "d" in blab);
>>true false true true

I’m assuming this is what you want to do. If not, please let me know.