Almost hitting the mark with almost 100% accuracy, Pumbaa80's Answer just missed mentioning one important detail. Certain iOS releases have a third digit included in them.

For instance:

Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_3 like Mac OS X; en_us) AppleWebKit/525.18.1 (KHTML, like Gecko)

The following code snippet allows for this scenario:

if(/(iPhone|iPod|iPad)/i.test(navigator.userAgent)) { 
    if(/OS [2-4]_\d(_\d)? like Mac OS X/i.test(navigator.userAgent)) {  
        // Handling iOS versions 2-4   
    } else if(/CPU like Mac OS X/i.test(navigator.userAgent)) {
        // For iOS version 1
    } else {
        // No action required for iOS 5 or newer
    }
}

By including (_\d)?, it accounts for the possibility of a third digit in the Version number. This should also provide clarity to Charlie S's query.

It's essential to note the presence of the 'else' statement due to the initial check being ineffective on iOS 1. In case of iOS 1 for iPhone and iPod devices, the UserAgent string didn't feature a version number.

Example: iPhone v 1.0

Mozilla/5.0 (iPhone; U; CPU like Mac OS X; en) AppleWebKit/420+ (KHTML, like Gecko) Version/3.0 Mobile/1A543 Safari/419.3

iPod v1.1.3

Mozilla/5.0 (iPod; U; CPU like Mac OS X; en) AppleWebKit/420.1 (KHTML, like Gecko) Version/3.0 Mobile/4A93 Safari/419.3

All this detailed information is available at Apple's official website here.

After not finding exactly what I needed, I decided to gather inspiration from various sources online and piece together a solution. Hopefully, this method will prove helpful to others as well.

function getiOSVersion() { 
    if(navigator.userAgent.match(/ipad|iphone|ipod/i)){ //checks if the user is using an Apple device
    var iosInfo ={};
    iosInfo.UserAgent=navigator.userAgent;
    iosInfo.AsReported=(navigator.userAgent).match(/OS (\d)?\d_\d(_\d)?/i)[0];
    iosInfo.MajorRelease=(navigator.userAgent).match(/OS (\d)?\d_\d(_\d)?/i)[0].split('_')[0];
    iosInfo.FullRelease=(navigator.userAgent).match(/OS (\d)?\d_\d(_\d)?/i)[0].replace(/_/g,".");
    iosInfo.MajorReleaseNumeric=+(navigator.userAgent).match(/OS (\d)?\d_\d(_\d)?/i)[0].split('_')[0].replace("OS ","");
    iosInfo.FullReleaseNumeric=+(navigator.userAgent).match(/OS (\d)?\d_\d(_\d)?/i)[0].replace("_",".").replace("_","").replace("OS ","");  
    return(iosInfo);
    }
}

This function retrieves both the major release and full release numbers for iOS, allowing them to be returned either as strings or numbers.

Example User Agent String:

var iOS=getiOSVersion();
console.log(iOS.FullRelease); //returns "OS 6.1.3"
console.log(iOS.FullReleaseNumeric); //returns 6.13

console.log(iOS.MajorRelease); //returns "OS 6"
console.log(iOS.MajorReleaseNumeric); //returns 6

console.log(iOS.AsReported); //returns "OS 6_1_3"
console.log(iOS.UserAgent); //returns full user agent string

In the context of the question that was asked originally, this code could be implemented in the following way:

var iOS=getiOSVersion();
$(document).bind("scroll", function() {
    if(iOS){if(iOS.MajorReleaseNumeric < 5) {} 
    else {changeFooterPosition();}
    }
});   

Expanding on the response from Pumbaa80, it is important to consider that the version string could be represented as 4_0, 5_0_1, or even 4_0_4. Checking against [1-4]_/d (a single underscore followed by a number) may not provide sufficient validation. The provided JavaScript snippet has been effective for detecting iOS sub-versions ranging from 3 to 5:

if (/(iPhone|iPod|iPad)/i.test(navigator.userAgent)) {
    if (/OS [1-4](.*) like Mac OS X/i.test(navigator.userAgent)) {
      // iOS version is <= 4.
    } else {
      // iOS version is > 4.
    }
  }

Below is a JavaScript snippet that can determine the version of iOS and Android operating systems.

This code has been tested with real user agent strings for iOS versions 4.3 to 6.0.1, and Android versions 2.3.4 to 4.2

var userOS;    // will be either iOS, Android, or unknown
var userOSver; // this will be a string, you can use Number(userOSver) to convert it to a number

function getOS( )
{
  var ua = navigator.userAgent;
  var uaindex;

  // determining OS
  if (ua.match(/iPad/i) || ua.match(/iPhone/i))
  {
    userOS = 'iOS';
    uaindex = ua.indexOf('OS');
  }
  else if (ua.match(/Android/i))
  {
    userOS = 'Android';
    uaindex = ua.indexOf('Android ');
  }
  else
  {
    userOS = 'unknown';
  }

  // determining version
  if (userOS === 'iOS' && uaindex > -1)
  {
    userOSver = ua.substr(uaindex + 3, 3).replace('_', '.');
  }
  else if (userOS === 'Android' && uaindex > -1)
  {
    userOSver = ua.substr(uaindex + 8, 3);
  }
  else
  {
    userOSver = 'unknown';
  }
}

To detect a specific version and higher, you can use:

if (userOS === 'iOS' && Number(userOSver.charAt(0)) >= 5 ) { ... }

Tip One: Avoid using match when a simple test will suffice.

Tip Two: Start by identifying the user agents known to have issues.

if(/(iPhone|iPod|iPad)/i.test(navigator.userAgent)) {
    if (/OS [1-4]_\d like Mac OS X/i.test(navigator.userAgent)) {
        changeFooterPosition();
...

function fetchIOSVersion() {
    const agent = navigator.userAgent;
    if (/(iPhone|iPod|iPad)/i.test(agent)) {
        return agent.match(/OS [\d_]+/i)[0].substr(3).split('_').map(num => parseInt(num));
    }
    return [0];
}

This function will retrieve an array containing the specific version numbers such as [10,0,1] for v10.0.1, or it will default to [0] if not iOS device is detected. You have the option to check the major version digit or all of them based on your requirements.

To check the operating system version of an iPhone, you can simply execute this code on your device or browser:

    const userAgent = window.navigator.userAgent;
    if(userAgent.match( /iP(hone|od|ad)/)){
        /* Example userAgent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 Mobile/15E148 Safari/604.1 */
        
        const iphone_version = userAgent.match(/OS [\d_]+/i)[0].substr(3).replace('_', '.');
        console.log(iphone_version); // This will output 16.6
    }

The variable `iphone_version` will accurately provide the iOS version for any iPhone model.

Separate the version number ("5") even more, and set a rule that triggers if the number surpasses or falls below the specified version.