How to add a spinner icon to button when it's in the Loading state?

Question

Simple solution for Bootstrap 3 using CSS3 animations.

Put the following in your CSS:

.glyphicon.spinning {
    animation: spin 1s infinite linear;
    -webkit-animation: spin2 1s infinite linear;
}

@keyframes spin {
    from { transform: scale(1) rotate(0deg); }
    to { transform: scale(1) rotate(360deg); }
}

@-webkit-keyframes spin2 {
    from { -webkit-transform: rotate(0deg); }
    to { -webkit-transform: rotate(360deg); }
}

Then just add the spinning class to a glyphicon while loading to get your spinning icon:

<button class="btn btn-lg btn-warning">
    <span class="glyphicon glyphicon-refresh spinning"></span> Loading...    
</button>

Based on http://www.bootply.com/128062#

• Note: IE9 and below do not support CSS3 animations.

If you look at the bootstrap-button.js source, you'll see that the bootstrap plugin replaces the buttons inner html with whatever is in data-loading-text when calling $(myElem).button('loading').

For your case, I think you should just be able to do this:

<button type="button"
        class="btn btn-primary start"
        id="btnStartUploads"
        data-loading-text="<i class='icon-spinner icon-spin icon-large'></i> @Localization.Uploading">
    <i class="icon-upload icon-large"></i>
    <span>@Localization.StartUpload</span>
</button>

There's now a full-fledged plugin for that:

http://msurguy.github.io/ladda-bootstrap/

To make the solution by @flion look really great, you could adjust the center point for that icon so it doesn't wobble up and down. This looks right for me at a small font size:

.glyphicon-refresh.spinning {
  transform-origin: 48% 50%;
}

A lazy way to do this is with the UTF-8 entity code for a half circle \25E0 (aka ◠), which looks like ◠ and then keyframe animate it. It's a simple as:

.busy
{
animation: spin 1s infinite linear;
display:inline-block;
font-weight: bold;
font-family: sans-serif;
font-size: 35px;
font-style:normal;
color:#555;
}

.busy::before
{
content:"\25E0";
}

@keyframes spin
{
0% {transform: rotate(0deg);}
100% {transform: rotate(359deg);}
}

<i class="busy"></i>

Here's my solution for Bootstrap 4:

<button id="search" class="btn btn-primary" 
data-loading-text="<i class='fa fa-spinner fa-spin fa-fw' aria-hidden='true'></i>Searching">
  Search
</button>

var setLoading = function () {
  var search = $('#search');
  if (!search.data('normal-text')) {
    search.data('normal-text', search.html());
  }
  search.html(search.data('loading-text'));
};

var clearLoading = function () {
  var search = $('#search');
  search.html(search.data('normal-text'));
};

setInterval(() => {
  setLoading();
  setTimeout(() => {
    clearLoading();
  }, 1000);
}, 2000);

Check it out on JSFiddle

These are mine, based on pure SVG and CSS animations. Don't pay attention to JS code in the snippet bellow, it's just for demoing purposes. Feel free to make your custom ones basing on mine, it's super easy.

var svg = d3.select("svg"),
    columnsCount = 3;

['basic', 'basic2', 'basic3', 'basic4', 'loading', 'loading2', 'spin', 'chrome', 'chrome2', 'flower', 'flower2', 'backstreet_boys'].forEach(function(animation, i){
  var x = (i%columnsCount+1) * 200-100,
      y = 20 + (Math.floor(i/columnsCount) * 200);
  
  
  svg.append("text")
    .attr('text-anchor', 'middle')
    .attr("x", x)
    .attr("y", y)
    .text((i+1)+". "+animation);
  
  svg.append("circle")
    .attr("class", animation)
    .attr("cx",  x)
    .attr("cy",  y+40)
    .attr("r",  16)
});

circle {
  fill: none;
  stroke: #bbb;
  stroke-width: 4
}

.basic {
  animation: basic 0.5s linear infinite;
  stroke-dasharray: 20 80;
}

@keyframes basic {
  0%    {stroke-dashoffset: 100;}
  100%  {stroke-dashoffset: 0;}
}

.basic2 {
  animation: basic2 0.5s linear infinite;
  stroke-dasharray: 80 20;
}

@keyframes basic2 {
  0%    {stroke-dashoffset: 100;}
  100%  {stroke-dashoffset: 0;}
}

.basic3 {
  animation: basic3 0.5s linear infinite;
  stroke-dasharray: 20 30;
}

@keyframes basic3 {
  0%    {stroke-dashoffset: 100;}
  100%  {stroke-dashoffset: 0;}
}

.basic4 {
  animation: basic4 0.5s linear infinite;
  stroke-dasharray: 10 23.3;
}

@keyframes basic4 {
  0%    {stroke-dashoffset: 100;}
  100%  {stroke-dashoffset: 0;}
}

.loading {
  animation: loading 1s linear infinite;
  stroke-dashoffset: 25;
}

@keyframes loading {
  0%    {stroke-dashoffset: 0;    stroke-dasharray: 50 0; }
  50%   {stroke-dashoffset: -100; stroke-dasharray: 0 50;}
  100%  { stroke-dashoffset: -200;stroke-dasharray: 50 0;}
}

.loading2 {
  animation: loading2 1s linear infinite;
}

@keyframes loading2 {
  0% {stroke-dasharray: 5 28.3;   stroke-dashoffset: 75;}
  50% {stroke-dasharray: 45 5;    stroke-dashoffset: -50;}
  100% {stroke-dasharray: 5 28.3; stroke-dashoffset: -125; }
}

.spin {
  animation: spin 1s linear infinite;
  stroke-dashoffset: 25;
}

@keyframes spin {
  0%    {stroke-dashoffset: 0;    stroke-dasharray: 33.3 0; }
  50%   {stroke-dashoffset: -100; stroke-dasharray: 0 33.3;}
  100%  { stroke-dashoffset: -200;stroke-dasharray: 33.3 0;}
}

.chrome {
  animation: chrome 2s linear infinite;
}

@keyframes chrome {
  0%    {stroke-dasharray: 0 100; stroke-dashoffset: 25;}
  25%   {stroke-dasharray: 75 25; stroke-dashoffset: 0;}
  50%   {stroke-dasharray: 0 100;  stroke-dashoffset: -125;}
  75%    {stroke-dasharray: 75 25; stroke-dashoffset: -150;}
  100%   {stroke-dasharray: 0 100; stroke-dashoffset: -275;}
}

.chrome2 {
  animation: chrome2 1s linear infinite;
}

@keyframes chrome2 {
  0%    {stroke-dasharray: 0 100; stroke-dashoffset: 25;}
  25%   {stroke-dasharray: 50 50; stroke-dashoffset: 0;}
  50%   {stroke-dasharray: 0 100;  stroke-dashoffset: -50;}
  75%   {stroke-dasharray: 50 50;  stroke-dashoffset: -125;}
  100%  {stroke-dasharray: 0 100;  stroke-dashoffset: -175;}
}

.flower {
  animation: flower 1s linear infinite;
}

@keyframes flower {
  0%    {stroke-dasharray: 0  20; stroke-dashoffset: 25;}
  50%   {stroke-dasharray: 20 0;  stroke-dashoffset: -50;}
  100%  {stroke-dasharray: 0 20;  stroke-dashoffset: -125;}
}

.flower2 {
  animation: flower2 1s linear infinite;
}

@keyframes flower2 {
  0%    {stroke-dasharray: 5 20;  stroke-dashoffset: 25;}
  50%   {stroke-dasharray: 20 5;  stroke-dashoffset: -50;}
  100%  {stroke-dasharray: 5 20;  stroke-dashoffset: -125;}
}

.backstreet_boys {
  animation: backstreet_boys 3s linear infinite;
}

@keyframes backstreet_boys {
  0%    {stroke-dasharray: 5 28.3;  stroke-dashoffset: -225;}
  15%    {stroke-dasharray: 5 28.3;  stroke-dashoffset: -300;}
  30%   {stroke-dasharray: 5 20;  stroke-dashoffset: -300;}
  45%    {stroke-dasharray: 5 20;  stroke-dashoffset: -375;}
  60%   {stroke-dasharray: 5 15;  stroke-dashoffset: -375;}
  75%    {stroke-dasharray: 5 15;  stroke-dashoffset: -450;}
  90%   {stroke-dasharray: 5 15;  stroke-dashoffset: -525;}
  100%   {stroke-dasharray: 5 28.3;  stroke-dashoffset: -925;}
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.13.0/d3.min.js"></script>
<svg width="600px" height="700px"></svg>

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