# getRandomElementFromArray

function getRandomElementFromArray(array: TArray, {filter?, associatedWeights?}: IParams)<T>: T;

Description:
Returns a random element of the array with the ability to determine the probability of each element relative to the others

type TArray = T[];
interface IParams {
   filter: (item: T) => boolean;
   associatedWeights: number[]; // There must be a weight for each element of the array
}

# Example

const array = [artifact1, artifact2];
const associatedWeights = [30_000, Number.MAX_SAFE_INTEGER];

const artifact = getRandomElementFromArray(array, {associatedWeights});
artifact // Is always artifact2
array // [artifact1] — artifact2 is sliced

# Real example

There are many events happening and we need to generate them according to the instantly changing context, with different probabilities for each one.
The confusing "event" has been replaced by "artifact".

interface IArtifactItem<M = {}> {
    id: ArtifactEnum;
    metadata?: IArtifactMetadata<M>;
}

interface IArtifactMetadata<M> {
    weight: number;
    canRepeat: boolean;
    ...M
}


const pull = [...ArtifactItemsCollection.values()]
    .map(item => ArtifactsCollection.get(item.id).fillItemWithMetadata(item, context))
    .filter(({id}) => ArtifactsCollection.get(id).isAvailableIn(item, context));

context.setPullData(pull, associatedWeights);

const associatedWeights = pull.map(item => item.metadata.weights);
for (let i = 0; i < context.userReceiveArtifactCount; i++){
    // Use typescript generic* for metadata
    const item = Util.getRandomElementFromArray<IArtifactItem>(pull, {associatedWeights});
    if (!item){
      continue;
    }

    if (!item.metadata.canRepeat){
        const index = pull.indexOf(event);
        if (~index){
            pull.splice(index, 1);
            associatedWeights.splice(index, 1);
        } 
    }

    const artifact = ArtifactsCollection.get(item.id);

    try {
        artifact.onReceived(item, context);
    }
    catch(error){
        ErrorHandler.write(error, {source: Errors.UserArtifactReceive, data: {itemId: item.id}});
    }


    context.user.artifacts.push(item);
}

# getRandomElementIndexInWeights

function getRandomElementIndexInWeights(weights: TWeights): number[];

Params:

type TWeights = NonNullable<IParams["associatedWeights]>

Description:
Returns the numeric index of the random element. The probability depends directly on the value of the element.

# Example

const tickets = [1, 5, 15, 50];
const index = getRandomElementIndexInWeights(tickets);

// index === 0: P = 1  / 71
// index === 1: P = 5  / 71
// index === 2: P = 15 / 71
// index === 3: P = 50 / 71

# Real example

// from getRandomElementFromArray source
const index = associatedWeights
    ? getRandomElementIndexInWeights(associatedWeights)
    : getRandomNumberInRange({ max: array.length });