rs-react-native-image-gallery/src/_helpers.ts

React Native Image Gallery with Thumbnails

import { NativeTouchEvent } from 'react-native';

/**
 * Calculate squared distance between two points
 * @param a First coordinate
 * @param b Second coordinate
 */
export const pow2abs = (a: number, b: number): number => (a - b) ** 2;

/**
 * Get distance between two touch points
 * @param touches Array of touch events
 */
export const getDistance = (touches: Array<NativeTouchEvent>): number => {
	// Early validation
	if (!touches || touches.length < 2) return 0;

	const [a, b] = touches;

	// Null check with optional chaining
	if (!a?.pageX || !b?.pageX || !a?.pageY || !b?.pageY) return 0;

	return Math.sqrt(pow2abs(a.pageX, b.pageX) + pow2abs(a.pageY, b.pageY));
};

/**
 * Calculate scale based on distance ratio with a multiplier
 * @param currentDistance Current distance between touch points
 * @param initialDistance Initial distance between touch points
 */
export const getScale = (currentDistance: number, initialDistance: number): number => {
	// Prevent division by zero
	if (!initialDistance) return 1;

	return (currentDistance / initialDistance) * 1.2;
};