javascript – Can I change the viewport meta tag in mobile safari on the fly?-ThrowExceptions

Exception or error:

I have an AJAX app built for mobile Safari browser that needs to display different types of content.

For some content, I need user-scalable=1 and for other ones, I need user-scalable=0.

Is there a way to modify the value of the content attribute without refreshing the page?

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

I realize this is a little old, but, yes it can be done. Some javascript to get you started:

viewport = document.querySelector("meta[name=viewport]");
viewport.setAttribute('content', 'width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0');

Just change the parts you need and Mobile Safari will respect the new settings.

Update:

If you don’t already have the meta viewport tag in the source, you can append it directly with something like this:

var metaTag=document.createElement('meta');
metaTag.name = "viewport"
metaTag.content = "width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"
document.getElementsByTagName('head')[0].appendChild(metaTag);

Or if you’re using jQuery:

$('head').append('<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">');

###

in your <head>

<meta id="viewport"
      name="viewport"
      content="width=1024, height=768, initial-scale=0, minimum-scale=0.25" />

somewhere in your javascript

document.getElementById("viewport").setAttribute("content",
      "initial-scale=0.5; maximum-scale=1.0; user-scalable=0;");

… but good luck with tweaking it for your device, fiddling for hours… and i’m still not there!

source

###

This has been answered for the most part, but I will expand…

Step 1

My goal was to enable zoom at certain times, and disable it at others.

// enable pinch zoom
var $viewport = $('head meta[name="viewport"]');    
$viewport.attr('content', 'width=device-width, initial-scale=1, maximum-scale=4');

// ...later...

// disable pinch zoom
$viewport.attr('content', 'width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no');

Step 2

The viewport tag would update, but pinch zoom was still active!! I had to find a way to get the page to pick up the changes…

It’s a hack solution, but toggling the opacity of body did the trick. I’m sure there are other ways to accomplish this, but here’s what worked for me.

// after updating viewport tag, force the page to pick up changes           
document.body.style.opacity = .9999;
setTimeout(function(){
    document.body.style.opacity = 1;
}, 1);

Step 3

My problem was mostly solved at this point, but not quite. I needed to know the current zoom level of the page so I could resize some elements to fit on the page (think of map markers).

// check zoom level during user interaction, or on animation frame
var currentZoom = $document.width() / window.innerWidth;

I hope this helps somebody. I spent several hours banging my mouse before finding a solution.

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