Question

How does one select DOM elements in javascript?
Like for example:

<div class="des">
    <h1>Test</h1>
        <div class="desleft">
          <p>Lorem Ipsum.</p>
        </div>
        <div class="Right">
           <button>Test</button>
        </div>
</div>

Now how do i select h1? This is just a part of a bigger Page, so cannot use getElementsByTagName(), since others might get selected. Also since there might be other h1‘s in the document later, i cannot attach the index(body’s) to above.

Is there a simple way to select, say <h1> tag which is under the classname of desleft?
I cannot use jQuery or any other libraries.

Answer 1

getElementsByTag()

Would be a function that you can start with, and then you can filter for the DOMElements that have the class.

var h1_array = document.getElementsByTag('h1');

var h1_class_array = [];
for (var i=0, len=h1_array.length; i < len; i++) {
    if (h1_array[i].className.indexOf('classname') !== -1) {
        h1_class_array.push(h1_array[i]);
    }
}

The .indexOf function returns -1 if the needle is not found in the haystack.

Now re-reading your question, why not just give your h1’s id’s ?

DOM traversal is one of javascript’s glaring issues (enter jQuery).

a simple getElementById() would save you a headache, and ids on all your h1’s would be much cleaner in the end than trying to formulate an algorithm to select them by other means.