You can use jQuery's attr() function. For example, if your img tag has an id attribute of 'my_image', you would do this:

<img id="my_image" src="first.jpg" alt="Insert link 1 alt text here" />

Then you can change the src of your image with jQuery like this:

$("#my_image").attr("src","second.jpg");

To attach this to a click event, you could write:

$('#my_image').on({
    'click': function(){
        $('#my_image').attr('src','second.jpg');
    }
});

To rotate the image, you could do this:

$('img').on({
    'click': function() {
         var src = ($(this).attr('src') === 'img1_on.jpg')
            ? 'img2_on.jpg'
            : 'img1_on.jpg';
         $(this).attr('src', src);
    }
});

One of the common mistakes people do when change the image source is not waiting for image load to do afterward actions like maturing image size etc. You will need to use jQuery .load() method to do stuff after image load.

$('yourimageselector').attr('src', 'newsrc').load(function(){
    this.width;   // Note: $(this).width() will not work for in memory images

});

Reason for editing: https://stackoverflow.com/a/670433/561545

In case you update the image multiple times and it gets CACHED and does not update, add a random string at the end:

// update image in dom
$('#target').attr('src', 'https://example.com/img.jpg?rand=' + Math.random());

Hope this can work

<img id="dummyimage" src="http://dummyimage.com/450x255/" alt="" />
<button id="changeSize">Change Size</button>

$(document).ready(function() {
    var flag = 0;
    $("button#changeSize").click(function() {
        if (flag == 0) {
            $("#dummyimage").attr("src", "http://dummyimage.com/250x155/");
            flag = 1;
        } else if (flag == 1) {
            $("#dummyimage").attr("src", "http://dummyimage.com/450x255/");
            flag = 0;
        }
    });
});

You should add id attribute to your image tag, like this:

<div id="d1">
   <div class="c1">
            <a href="#"><img id="img1" src="img1_on.gif"></a>
            <a href="#"><img id="img2" src="img2_on.gif"></a>
   </div>
</div>

then you can use this code to change the source of images:

 $(document).ready(function () {
        $("#img1").attr({ "src": "logo-ex-7.png" });
        $("#img2").attr({ "src": "logo-ex-8.png" });
    });

Change the image source using jQuery click()

element:

    <img class="letstalk btn"  src="images/chatbuble.png" />

code:

    $(".letstalk").click(function(){
        var newsrc;
        if($(this).attr("src")=="/images/chatbuble.png")
        {
            newsrc="/images/closechat.png";
            $(this).attr("src", newsrc);
        }
        else
        {
            newsrc="/images/chatbuble.png";
            $(this).attr("src", newsrc);
        }
    });

I made a codepen with exactly this functionality here. I will give you a breakdown of the code here as well.

Codepen

$(function() {

  //Listen for a click on the girl button
  $('#girl-btn').click(function() {

    // When the girl button has been clicked, change the source of the #square image to be the girl PNG
    $('#square').prop("src", "https://homepages.cae.wisc.edu/~ece533/images/girl.png");
  });

  //Listen for a click on the plane button
  $('#plane-btn').click(function() {

    // When the plane button has been clicked, change the source of the #square image to be the plane PNG
    $('#square').prop("src", "https://homepages.cae.wisc.edu/~ece533/images/airplane.png");
  });

  //Listen for a click on the fruit button
  $('#fruits-btn').click(function() {

    // When the fruits button has been clicked, change the source of the #square image to be the fruits PNG
    $('#square').prop("src", "https://homepages.cae.wisc.edu/~ece533/images/fruits.png");
  });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>


<img src="https://homepages.cae.wisc.edu/~ece533/images/girl.png" id="square" />
<div>
  <button id="girl-btn">Girl</button>
  <button id="plane-btn">Plane</button>
  <button id="fruits-btn">Fruits</button>

  <a href="https://homepages.cae.wisc.edu/~ece533/images/">Source of Images</a>
</div>

This is a guaranteed way to get it done in Vanilla (or simply Pure) JavaScript:

var picurl = 'pictures/apple.png';
document.getElementById("image_id").src=picurl;

Just an addition, to make it even more tiny:

$('#imgId').click(function(){
    $(this).attr("src",$(this).attr('src') == 'img1_on.gif' ? 'img1_off.gif':'img1_on.gif');
});

Short but exact

$("#d1 img").click(e=> e.target.src= pic[e.target.src.match(pic[0]) ? 1:0] );

let pic=[
  "https://picsum.photos/id/237/40/40", // arbitrary - eg: "img1_on.gif",
  "https://picsum.photos/id/238/40/40", // arbitrary - eg: "img2_on.gif"
];

$("#d1 img").click(e=> e.target.src= pic[e.target.src.match(pic[0]) ? 1:0] );

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div id="d1">
   <div class="c1">
            <a href="#"><img src="img1_on.gif"></a>
            <a href="#"><img src="img2_on.gif"></a>
   </div>
</div>