如何在单击enter / return期间更改contenteditable html元素的默认行为？

Question

I've found out during clicking either enter or return on the contenteditable p element it gets extended with new div or p. I'd llike it is being extended with only br. I've tried below page , but it's not working.

document.execCommand("defaultParagraphSeparator" , false , "br");

https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Editable_content

document.onreadystatechange = function(){
        if(document.readyState == 'complete'){
            document.execCommand("defaultParagraphSeparator" , false , "br");
        }
    }


function public_mode(){
    var key = window.event.keyCode;
    if (key == 13) {
        sendMessage();
    }

}

function sendMessage(){
    var content = document.getElementById("content");
    console.log(content.innerHTML);
}
<p id = "content" contenteditable="true" onkeypress="public_mode()"></p>    

//p content is:
Hello world!
Hello world!

//console result is:
Hello world!
Hello world!<div>Hello world!</div>

Answer 1

It actually appears, based on the article you linked, that this is only possible in Firefox

Additionally, Firefox supports non-standard argument, br, for defaultParagraphSeparator since Firefox 55. This is really useful if your web application supports the older Firefox behavior with checking whether the browser is Firefox and unfortunately, you don't have much time to fix your web application for newer Firefox, you can take the older Firefox behavior back with inserting this line when you initializes designMode or contenteditable editor