Changing the keypress

Question

In an input box or contenteditable=true div, how can I modify a keypress for the letter \"a\" to return a keybress for the letter \"b\"? I.e., every time you type the letter

Answer 1

Here a simple example to replace , to . using Vanilla JavaScript

// change ',' to '.'
document.getElementById('only_float').addEventListener('keypress', function(e){
    if (e.key === ','){
        // get old value
        var start = e.target.selectionStart;
        var end = e.target.selectionEnd;
        var oldValue = e.target.value;

        // replace point and change input value
        var newValue = oldValue.slice(0, start) + '.' + oldValue.slice(end)
        e.target.value = newValue;

        // replace cursor
        e.target.selectionStart = e.target.selectionEnd = start + 1;

        e.preventDefault();
    }
})