// 计算两个迪卡尔坐标之间的距离
function distance(x1, y1, x2, y2) {
	let dx = x2 - x1;
	let dy = y2 - y1;
	return Math.sqrt(dx * dx + dy * dy);
}
console.log(distance(1, 2, 8, 9)) // => 9.899494936611665