const ele = document.getElementById('message');

​

ele.addEventListener('keydown', function (e) {

    // Get the code of pressed key

    const keyCode = e.which || e.keyCode;

​

    // 13 represents the Enter key

    if (keyCode === 13 && !e.shiftKey) {

        // Don't generate a new line

        e.preventDefault();

​

        // Do something else such as send the message to back-end

        // ...

    }

});