how to replace br with newline in javascript code example

Example 1: javascript replace line breaks with br

function nl2br(str){
 return str.replace(/(?:\r\n|\r|\n)/g, '<br>');
}
var stringWithNewLines= `Well this is a
a very broken
sentance`;
var stringWithBrs=nl2br(stringWithNewLines);
// stringWithBrs= "Well this is a<br>a very <br>broken<br>sentance"

Example 2: javascript replace with n

var str = $("#mydiv").html();
var regex = /<br\s*[\/]?>/gi;
$("#mydiv").html(str.replace(regex, "\n"));