iOS10之前

<meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0;" name="viewport" />

iOS10之后

window.onload = function() {
    // 阻止双击放大
    let lastTouchEnd = 0;
    document.addEventListener('touchstart', function(event) {
        if (event.touches.length > 1) {
            event.preventDefault();
        }
    });
    document.addEventListener('touchend', function(event) {
        let now = (new Date()).getTime();
        if (now - lastTouchEnd <= 300) {
            event.preventDefault();
        }
        lastTouchEnd = now;
    }, false);

    // 阻止双指放大
    document.addEventListener('gesturestart', function(event) {
        event.preventDefault();
    });
}