jquery.adjust-viewport.js

function adjustViewport( property, value )
{
  var
  $viewport = $('meta[name=viewport]'),
  currently = $viewport.attr('content'),
  o_props   = currently.split(/\s,\s?/),
  n_props   = [],
  i         = o_props.length,
  set       = false;
  while ( i-- )
  {
    o_props[i] = o_props[i].split(/\s?=\s?/);
    if ( o_props[i][0] == property )
    {
      if ( value !== false )
      {
        o_props[i][1] = value;
        n_props.push( o_props[i].join('=') );
      }
      set = true;
    }
    else
    {
      n_props.push( o_props[i].join('=') );
    }
  }
  if ( ! set )
  {
    n_props.push(property+'='+value);
  }
  n_props = n_props.join(',');
  $viewport.attr('content',n_props);
}