https://thecharcoalkebabhouse.co.uk/assets/js/ios-viewport-fix.js

1// This function was made to stop IOS zoom (IOS overrides them due to accessibility). This means if maxiumum-scale is set for all devices,
2// pinch to zoom is entirely disabled on Chrome and Firefox for Android. 
3
4// An Alternative solution would be to ensure all relevent input fontsizes are atleast 16px. However, due to time constraints, this approach was used, as many areas of 
5// application are currently below 14px font size and would require redesigning.
6(function () {
7    'use strict';
8
9    var isIOS = /iPad|iPhone|iPod/.test(navigator.userAgent) || (navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1);
10
11    if(!isIOS) {
12        return;
13    }
14
15    var viewport = document.getElementById('viewport-meta') || document.querySelector('meta[name="viewport"]');
16
17    if(!viewport) {
18        return;
19    }
20    
21    var content = viewport.getAttribute('content') || '';
22
23    if(content.indexOf('maximum-scale') === -1) {
24        viewport.setAttribute('content', content + ', maximum-scale=1.0');
25    }
26})();