js 图片触摸缩放

let initialDistance = 0;
let scale = 1;

const image = document.getElementById('image');

image.addEventListener('touchstart', function(event) {
    if (event.touches.length === 2) {
        initialDistance = Math.hypot(
            event.touches[0].pageX - event.touches[1].pageX,
            event.touches[0].pageY - event.touches[1].pageY
        );
    }
});

image.addEventListener('touchmove', function(event) {
    if (event.touches.length === 2) {
        const currentDistance = Math.hypot(
            event.touches[0].pageX - event.touches[1].pageX,
            event.touches[0].pageY - event.touches[1].pageY
        );
        scale = currentDistance / initialDistance;
        image.style.transform = `scale(${scale})`;
    }
});

image.addEventListener('touchend', function(event) {
    if (event.touches.length < 2) {
        initialDistance = 0;
        scale = 1;
    }
});