Question

i have a web app that run fluently on IOS 5 but it lags too much on IOS 4.

Is it possible to detect IOS 4 and lower to disable some functions ?

Answer 1

You can analyse the user agent string.

iOS 4 example (on iPad):

Mozilla/5.0 (iPad; U; CPU OS 4_3_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8G4 Safari/6533.18.5

iOS 5 example (on iPhone):

Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3

But if you want to do that using JavaScript, try:

if (navigator.userAgent.match(/OS 5_\d like Mac OS X/i))
    document.write("You are using iOS5");