js在已有元素之前新增一个元素，代码求助

Question

function preparePlaceholder(){
var placeholder=document.createElement("img");
placeholder.setAttribute("id","placeholder");
placeholder.setAttribute("src"，"image/36819566_1406607352178_medium.jpg");
placeholder.setAttribute("alt","my image gallery");
var description = document.createElement("p");
var txt= document.createTextNode("Choose an image");
description.setAttribute("id","description");
description.appendChild(txt);
document.getElementsByTagName("body")[0].appendChild(placeholder);
document.getElementsByTagName("body")[0].appendChild(description);
// var gallery = document.getElementById("imagegallery");
// gallery.parentNode.insertBefore(placeholder,gallery);
// gallery.parentNode.insertBefore(description,gallery);
}
preparePlaceholder();

Answer 1

placeholder.setAttribute("src"，"image/36819566_1406607352178_medium.jpg");

 placeholder.setAttribute("src"，"image/36819566_1406607352178_medium.jpg");

里面的逗号是全角符号，你检查一下，把 ， 换成 , 吧。