How do I dynamically populate html elements with JSON Data with Javascript not jQuery?

Question

I have this following JSON data snippit:

{"items": [
 {
   "title": "sample 1",
   "author": "author 1"
 },
 {
  "title": "sample 2",
  "author": "author 2"
 }
]}

How do I populate the following html elements with this data:

<div class="news-story">
 <h5>sample 1</h5>
 <p>By: author 1</p>
 <h5>sample 2</h5>
 <p>By: author 2</p>
</div>

I want accomplish this with Javascript not jQuery.

Answer 1

var div = document.getElementsByClassName('news-story')[0],
    h5 = div.getElementsByTagName('h5'),
    p = div.getElementsByTagName('p'),
    data = JSON.parse( my_JSON_data );

data.items.forEach(function(v,i) {
    h5[i].innerHTML = v.title;
    p[i].innerHTML = "By: " + v.author;
});

JSFIDDLE DEMO

---

If you need to support older browsers, you can use a typical for statement instead of the forEach method.

for( var i = 0; i < data.items.length; ++i ) {
    var v = data.items[i];
    h5[i].innerHTML = v.title;
    p[i].innerHTML = "By: " + v.author;
}

And I'd suggest using an ID instead of a class for the news-story element, so you can use getElementById instead (unless of course you have several of them).

If that's impossible, you may want to use a compatibility function from MDN for getElementsByClassName.

---

If you needed to create the inner elements, then here's one way:

var div = document.getElementsByClassName('news-story')[0],
    data = JSON.parse( my_JSON_data ),
    html;

html = data.items.map(function(v,i) {
    return '<h5>' + v.title + '</h5>' +
           '<p>By: ' + v.author + '</p>';
}).join('');

div.innerHTML = html;

JSFIDDLE DEMO

---

@Xeon06 shows how in his answer using createElement(), which is arguably a better approach.

Here's how I'd do it:

var div = document.getElementsByClassName('news-story')[0],
    frag = document.createDocumentFragment(),
    data = JSON.parse( my_JSON_data );

data.items.forEach(function(v,i) {
    frag.appendChild( document.createElement('h5') ).innerHTML = v.title;
    frag.appendChild( document.createElement('p') ).innerHTML = "By: " + v.author;
});
div.appendChild( frag );

JSFIDDLE DEMO

And of course you can modify it to use a for statement instead:

var div = document.getElementsByClassName('news-story')[0],
    frag = document.createDocumentFragment(),
    data = JSON.parse( my_JSON_data );

for( var i = 0; i < data.items.length; ++i ) {
    var v = data.items[i];
    frag.appendChild( document.createElement('h5') ).innerHTML = v.title;
    frag.appendChild( document.createElement('p') ).innerHTML = "By: " + v.author;
}
div.appendChild( frag );

The benefit of using a documentFragment is that you can do a single append to the DOM via the fragment instead of multiple appends. This gives better performance, especially if you have a large set of data.

Answer 2

Loop through them and use the DOM functions:

var news = document.getElementsByClassName("news-story")[0];
var items = json.items;
for(var i = 0; i < items.length; i++) {
    var h5 = document.createElement("h5");
    h5.innerHTML = items[i].title;
    news.appendChild(h5);
    var p = document.createElement("p");
    p.innerHTML = items[i].author;
    news.appendChild(p);

}

http://jsfiddle.net/AWRAW/

getElementsByClassName will not work in versions of IE prior to 9. If you need to support those though, you're really better off using jQuery.