How do I declare javascript search function if i only have class?

Question

I want to declare javascript to search based on the div class, however i could specify the code. Below is the javascript code im using.

function searchFunction()() {
  var input, filter, div, a;
  input = document.getElementById('myinput');
  filter = input.value.toUpperCase();
  div = document.getElementByClassName('panel panel-default')
  a = document.getElementsByTagName('accordion-toggle')

  for (i = 0; i < li.length; i++) {
    a = li[i].getElementsByTagName("a")[0];
    if (a.innerHTML.toUpperCase().indexOf(filter) > -1) {
      li[i].style.display = "";
    } else {
      li[i].style.display = "none";
    }
  }
}

header

<div class="container">
  <div class="panel-group" id="accordion">
    <div class="faqHeader">
      <font color="#008080"><strong><code class="border-rounded">General Questions</strong>
        <p style="text-align:center">
          </code>
      </font>
    </div>

Search function that i declare

    <input type="text" name="search" value="" autocomplete="off" id="myinput" onkeypress="searchFunction()" placeholder="Search...">

Content to be search when im inputing in search box

    <Form>
      <div class="panel panel-default">
        <div class="panel-heading">
          <h4 class="panel-title">
            <a class="accordion-toggle" data-toggle="collapse" data-parent="#accordion" href="#collapseOne"><strong>What do you like?</strong></a>
          </h4>
        </div>
        <div id="collapseOne" class="panel-collapse collapse in">
          <div class="panel-body">
            <p>I like potato</p>
          </div>
        </div>
      </div>
    </form>

Answer 1

You can use queryselector, this way:

document.querySelector(".some_class");