How can I count the number of true statements in a list?

Question

I have a dynamic layout within a React Native view - that changes based on provided data for the particular data set. Ie there could be a provided Guide, Inventory, or Observation list that need displaying - but there may just be a combination of one, two or 3 of these things provided within any dataset.

I need to supply conditional styles / display object throughout the view based on the state of each provided data type.

Currently I have a series of checks that return true if the state is populated i.e:

const hasSiteGuide = () => {
  if (!this.isEmpty(this.state.locationSiteGuidePdf)) {
    return true;
  }
};

I then have a series of functions that determine how many items are supplied and provide the relevant style - here are the logic checks:

 const layout_full = () => {
  if (hasSiteGuide() && hasInventoryItems() && hasObservations()) {
    return true;
  }
};
const layout_one = () => {
  if (!hasSiteGuide() && !hasInventoryItems() && !hasObservations()) {
    return true;
  }
};

const layout_two = () => {
      if (!hasSiteGuide() || !hasInventoryItems() !hasObservations()) {
        if (hasSiteGuide() || hasInventoryItems()) {
          return true;
        }
      }
    };

the checks are used to display conditional styles in multiple areas - for example:

 <View
              style={[
                layout_full() && RP_Styles.btnWrap,
                layout_three() && RP_Styles.btnWrap_three,
                layout_two() && RP_Styles.btnWrap_two,
                layout_one() && RP_Styles.btnWrap_one,
              ]}>

My question is - i'm sure that there is a better way to do this.. particularly as i'm about to implement a 4th possibility - I was wondering if there is a way that I could use just one function to count how many true statements are in a list and return the relevant condition

ie:

returnTrueCount(hasSiteGuide(), hasInventoryItems(), hasObservations()). - is this possible? Or has anybody got an idea for a better approach please? Thanks very much

Related: [count of specific values in array](https://stackoverflow.com/questions/37365512/count-the-number-of-times-a-same-value-appears-in-a-javascript-array). — jarmod, Sep 13 '21 at 16:24
Where are these functions coming from? Are the defined in the class? — h-sifat, Sep 13 '21 at 16:25
@Dancer but if they are in a class why they have `const` before them? — h-sifat, Sep 13 '21 at 16:33

score 1 · Answer 1 · answered Sep 13 '21 at 16:32

If you want do something like this : returnTrueCount(hasSiteGuide(), hasInventoryItems(), hasObservations()) then I think the following solution would would work.

const a = () => true;
const b = () => true;
const c = () => false;
const d = () => true;

function returnTrueCount(...funcs) {
  return funcs.reduce((a, f) => a + +f(), 0);
}

console.log(returnTrueCount(a, b, c, d));

score 1 · Answer 2 · answered Sep 20 '21 at 14:54

1

This worked for me:

    const returnTrueCount = (array, value) => {
      return array.filter((v) => v === value).length;
    };

called with a basic array and the value to check.

answered Sep 20 '21 at 14:54

Dancer

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How can I count the number of true statements in a list?

2 Answers2