how to change image class in jquery code example

Example 1: jquery change picture onclick

<!-- https://codepen.io/poliweb/pen/eYJNqLM -->
<!-- https://stackoverflow.com/questions/26377231/jquery-how-to-change-img-src-path-onclick -->

<div class="img-container">
  <img id="changeMe" src="">
</div>

<img class="preview" src="images/preview-1.jpg">
<img class="preview" src="images/preview-2.jpg">
<img class="preview" src="images/preview-2.jpg">
  
 <!-- Script --> 
  
  $('.preview').on('click',  function() {
    $('#changeMe').prop('src', this.src);
});

Example 2: jquery change picture source

// https://codepen.io/kman/pen/dXjpoX
// Stockphotos JS

$(document).ready(function(){
  var flag = 0;  
  $("button#changeSize").click(function(){
    if(flag == 0) {
      $("#dummyimage").attr("src","http://dummyimage.com/350x155/");
      flag = 1;
    }
    else if(flag == 1) {
      $("#dummyimage").attr("src","http://dummyimage.com/450x255/");
      flag = 0;
    }
  });
});