Javascript clipboard.readText() not working in IOS Safari?

I have lines:

$(document).ready(function(){
        $(window).on('focus', function () {
            navigator.clipboard.readText().then(q => {
                alert(q);   
            }).catch(err => {
                console.error('Failed to read clipboard contents: ', err);
            });

         });
    });

Run well on Android's browser. But in IOS Safari, nothing happens. Please help !