const prepareArray = (items: Array<number>, medianValue: number, direction: number) => {
    const data = items.map((x) => x * direction > medianValue * direction ? x : null);

    const indexes = data.reduce((indexes: Array<number>, item, index) => {
       if (item) {
           if (data[index - 1] === null) indexes.push(index - 1);
           if (data[index + 1] === null) indexes.push(index);
       }
        return indexes;
    }, []);

    let indexOffset = 1;
    indexes.forEach(index => {
        data.splice(index + indexOffset, 0, medianValue);
        indexOffset++;
    });

    console.log(indexes);

    return data;
};

let testFunction = (items: Array<number>, medianValue: number) => {
    const hight = prepareArray(items, medianValue, 1);
    const low = prepareArray(items, medianValue, -1);
    return { hight, low };
};

 let data = testFunction([10, 40, 60, 70, 80, 90, 10, 10, 70, 80, 90], 50);
 console.log(data)