如何在使用innerHTML时添加逗号？

var content = "内容1, 内容2, 内容3";
var commaSeparatedContent = content.split(',').join(', ');
document.getElementById("elementId").innerHTML = commaSeparatedContent;

var content = "内容1, 内容2, 内容3";
var commaSeparatedContent = content.replace(/,/g, ', ');
document.getElementById("elementId").innerHTML = commaSeparatedContent;

var contentArray = ["内容1", "内容2", "内容3"];
var commaSeparatedContent = contentArray.join(', ');
document.getElementById("elementId").innerHTML = commaSeparatedContent;