How can I make the image appear in the container Div?

In simple terms, I have a javascript code that generates random images when the user clicks a button. It's a blank page with a button and a container div. The problem is that the image appears outside the container, directly before. and I need to control where it is displayed. I want to put it in a container. I'm not a JavaScript expert and I found the code after a long search. I need help, thanks :)

The code is here : https://codepen.io/Haitham1000/pen/aXjYzz

function display_random_image() 
{
var theImages = [{
src: "http://farm4.staticflickr.com/3691/11268502654_f28f05966c_m.jpg",
width: "240",
height: "160"
}, {
src: "http://farm1.staticflickr.com/33/45336904_1aef569b30_n.jpg",
width: "320",
height: "195"
}, {
src: "http://farm6.staticflickr.com/5211/5384592886_80a512e2c9.jpg",
width: "500",
height: "343"
}];

var preBuffer = [];
for (var i = 0, j = theImages.length; i < j; i++) {
preBuffer[i] = new Image();
preBuffer[i].src = theImages[i].src;
preBuffer[i].width = theImages[i].width;
preBuffer[i].height = theImages[i].height;
}

// create random image number
function getRandomInt(min,max) 
{
//  return Math.floor(Math.random() * (max - min + 1)) + min;

imn = Math.floor(Math.random() * (max - min + 1)) + min;
return preBuffer[imn];
}  

// 0 is first image,   preBuffer.length - 1) is  last image

var newImage = getRandomInt(0, preBuffer.length - 1);

// remove the previous images
var images = document.getElementsByTagName('img');
var l = images.length;
for (var p = 0; p < l; p++) {
images[0].parentNode.removeChild(images[0]);
}
// display the image  
var targetContainer = document.getElementsByClassName("container");
targetContainer[0].appendChild(newImage);
}