rn-zoomable/helpers/getDistance.js

A zoomable image component like Instagram

// @flow
import type { Touch } from "../types/Touch";

export function pow2abs(a: number, b: number) {
  return Math.pow(Math.abs(a - b), 2);
}

function getDistance(touches: Array<Touch>) {
  const [a, b] = touches;
  if (a == null || b == null) {
    return 0;
  }
  return Math.sqrt(pow2abs(a.pageX, b.pageX) + pow2abs(a.pageY, b.pageY));
}

export default getDistance;