how to change source of image in jquery code example

Example 1: jquery change image src

//change image src with jquery
$("#myImageID").attr("src","images/my_other_image.png");

//change image src plain javascript
document.getElementById('myImageID').src="images/my_other_image.png";

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;
    }
  });
});