function resolveBoxStyle(
  prefix: string,
  style: Object,
): BoxStyle | null {
  let hasParts = false;
  const result = {
    bottom: 0,
    left: 0,
    right: 0,
    top: 0,
  };

  const styleForAll = style[prefix];
  if (styleForAll != null) {
    // eslint-disable-next-line no-for-of-loops/no-for-of-loops
    for (const key of Object.keys(result)) {
      result[key] = styleForAll;
    }
    hasParts = true;
  }

  const styleForHorizontal = style[prefix + 'Horizontal'];
  if (styleForHorizontal != null) {
    result.left = styleForHorizontal;
    result.right = styleForHorizontal;
    hasParts = true;
  } else {
    const styleForLeft = style[prefix + 'Left'];
    if (styleForLeft != null) {
      result.left = styleForLeft;
      hasParts = true;
    }

    const styleForRight = style[prefix + 'Right'];
    if (styleForRight != null) {
      result.right = styleForRight;
      hasParts = true;
    }

    const styleForEnd = style[prefix + 'End'];
    if (styleForEnd != null) {
      // TODO RTL support
      result.right = styleForEnd;
      hasParts = true;
    }
    const styleForStart = style[prefix + 'Start'];
    if (styleForStart != null) {
      // TODO RTL support
      result.left = styleForStart;
      hasParts = true;
    }
  }

  const styleForVertical = style[prefix + 'Vertical'];
  if (styleForVertical != null) {
    result.bottom = styleForVertical;
    result.top = styleForVertical;
    hasParts = true;
  } else {
    const styleForBottom = style[prefix + 'Bottom'];
    if (styleForBottom != null) {
      result.bottom = styleForBottom;
      hasParts = true;
    }

    const styleForTop = style[prefix + 'Top'];
    if (styleForTop != null) {
      result.top = styleForTop;
      hasParts = true;
    }
  }

  return hasParts ? result : null;
}
This mirrors react-native/Libraries/Inspector/resolveBoxStyle.js (but without RTL support).

Resolve a style property into it's component parts, e.g.

resolveBoxStyle('margin', {margin: 5, marginBottom: 10})
-> {top: 5, left: 5, right: 5, bottom: 10}