Enable/disable zoom on iPhone safari with Javascript?

Question

I have 1 page which has 2 DIV elements which is shown/hidden based on user click on action buttons with javascript, I would like to toggle scaling on action button click.

I tried with below javascript and it is changing viewport meta but getting no effect.

Any suggestions?

var ViewPortAllowZoom = 'width=device-width;';

var ViewPortNoZoom = 'width=device-width; initial-scale=1.0; maximum-scale=1.0; minimum-scale=1.0; user-scalable=no;';

  function AllowZoom(flag) {
            if (flag == true) {
                $('meta[name*=viewport]').attr('content', ViewPortAllowZoom);                
            }
            else {
                $('meta[name*=viewport]').attr('content', ViewPortNoZoom);
            }
        }

Answer 1

Removing and re-adding the meta tag worked for me:

function AllowZoom(flag) {
  if (flag == true) {
    $('head meta[name=viewport]').remove();
    $('head').prepend('<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=10.0, minimum-scale=1, user-scalable=1" />');
  } else {
    $('head meta[name=viewport]').remove();
    $('head').prepend('<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=0" />');              
  }
}

However, if the user zooms in and then switches to no zoom, the viewport remains zoomed and the user can no longer change the zoom. Does anyone have a solution for that?

Answer 2

$('body').bind('touchmove', function(event) { event.preventDefault() }); // turns off

$('body').unbind('touchmove'); // turns on