react/components/slider/slider-mark.tsx

import React, { useMemo } from 'react'
import useTheme from '../styles/use-theme'

interface Props {
  max: number
  min: number
  step: number
}

export type MarkLeftValue = number

export type Marks = Array<MarkLeftValue>

const getMarks = (
  min: number,
  max: number,
  step: number,
): Marks => {
  const value = max - min
  const roundFunc = !(value % step) ? Math.floor : Math.ceil
  const count = roundFunc(value / step) - 1
  if (count >= 99) return []
  
  return [...new Array(count)]
    .map((_, index) => (step * (index + 1) * 100) / value)
}

const SliderMark: React.FC<React.PropsWithChildren<Props>> = ({
  step, max, min,
}) => {
  const theme = useTheme()
  const marks = useMemo(() => getMarks(min, max, step), [min, max, step])

  return (
    <>
      {marks.map((val, index) => (
        <span key={`${val}-${index}`} style={{ left: `${val}%` }} />
      ))}
      <style jsx>{`
        span {
          position: absolute;
          width: 2px;
          height: 100%;
          top: 50%;
          transform: translate(-50%, -50%);
          background-color: ${theme.palette.background};
        }
      `}</style>
    </>
  )
}

export default SliderMark