jquery find() equivalent for javascript

Question

I have three tables and i want to check wheter they contain a specific element, e.g. a button with the value 'Previous'. I solved it by using the jquery function find and writing a function, but i need to solve this problem without jquery. Is this possible?

var t1 = document.getElementById("table_one");
var t2 = document.getElementById("table_two");
var t3 = document.getElementById("table_three");

has_prev_button(t1);
has_prev_button(t2);
has_prev_button(t3);

function has_prev_button(element)
{
  var has_prev_button = false;
  var check = $(element).find("input[type=button]");
  
  for (i=0; i<=check.length-1; i++) {
    if (check[i].getAttribute("value") == "Previous") {
      has_prev_button = true;
    }
  }

  if (has_prev_button) {
    document.write("<p>The selected table has a Previous button</p>");
  } else {
    document.write("<strong><p style='color:red'>The selected table has NO Previous button</p></strong>");
  }
}

table {
  margin-bottom:40px;
  border: 1px solid black;
}

td {
  border: 2px solid #D8D8D8;
  width: 70px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table id="table_one">
  <tr>
    <td>Foo</td>
    <td>Bar</td>
  <tr>
  <tr>
    <td><input type="button" value="Previous"></td>
    <td><input type="button" value="Next"></td>
  </tr>
</table>

<table id="table_two">
  <tr>
    <td>Foo</td>
    <td>Bar</td>
  <tr>
  <tr>
    <td></td>
    <td><input type="button" value="Next"></td>
  </tr>
</table>

<table id="table_three">
  <tr>
    <td>Foo</td>
    <td>Bar</td>
  <tr>
  <tr>
    <td><input type="button" value="Previous"></td>
    <td><input type="button" value="Next"></td>
  </tr>
</table>

Answer 1

Use element.querySelectorAll:

var t1 = document.getElementById("table_one");
var t2 = document.getElementById("table_two");
var t3 = document.getElementById("table_three");

has_prev_button(t1);
has_prev_button(t2);
has_prev_button(t3);

function has_prev_button(element)
{
  var has_prev_button = false;
  var check = element.querySelectorAll("input[type=button]");
  
  for (i=0; i<=check.length-1; i++)
  {
    if (check[i].value == "Previous")
    {
      has_prev_button = true;
    }
  }

  if (has_prev_button)
  {
    document.write("<p>The selected table has a Previous button</p>");
  }
  else
  {
    document.write("<strong><p style='color:red'>The selected table has NO Previous button</p></strong>");
  }
}

table {
  margin-bottom:40px;
  border: 1px solid black;
}

td {
  border: 2px solid #D8D8D8;
  width: 70px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table id="table_one">
  <tr>
    <td>Foo</td>
    <td>Bar</td>
  <tr>
  <tr>
    <td><input type="button" value="Previous"></td>
    <td><input type="button" value="Next"></td>
  </tr>
</table>

<table id="table_two">
  <tr>
    <td>Foo</td>
    <td>Bar</td>
  <tr>
  <tr>
    <td></td>
    <td><input type="button" value="Next"></td>
  </tr>
</table>

<table id="table_three">
  <tr>
    <td>Foo</td>
    <td>Bar</td>
  <tr>
  <tr>
    <td><input type="button" value="Previous"></td>
    <td><input type="button" value="Next"></td>
  </tr>
</table>

Answer 2

Simply use document.querySelectorAll along with the classes spaced apart.

For example, if I want to find the button in the 3rd section and change its background color:

jQuery

$('.my_sections').eq(2).find('.my_button').css('background', 'pink')

Vanilla JS

document.querySelectorAll('.my_sections .my_button')[2].style.background = 'pink'

Similarly, If I wanted to check how many buttons I had of the my_button class:

document.querySelectorAll('.my_sections .my_button').length