Bootstrap mobile menu icon change to x close

Question

EDIT

@zim answer uses 2020 CSS to easily solve the issue and better applies to Bootstrap 4.

The original question and selected answer are still

Answer 1

The below code helps you to solve this issue.

Html:

Mobile Navigation menu using css and jquery

css:

.btn {
background-color: #ffd200;
color: #00174f;
display: inline-block;
text-decoration: none;
padding: 13px 30px;
margin: 30px 0 0 0;
border-radius: 3px;
font-weight: bold;
}
.btn:hover {
background-color: #fff;
}
.btn--transition {
-webkit-transition: -webkit-transform 0.2s;
-webkit-transition: all 200ms ease-in-out;
transition: all 200ms ease-in-out;
}
:focus {
outline: none;
}
.icons {
margin: 50px 0;
}
.icon {
margin: 0 30px 0 0;
}

.icon {
background-color: #ff3000;
border: 0;
height: 79px;
width: 79px;
border-radius: 50%;
cursor: pointer;
position: relative;
}
.icon span {
display: block;
height: 5px;
width: 33px;
background-color: #ffffff;
border-radius: 2px;
position: absolute;
left: 23px;
-webkit-transition: -webkit-transform 0.3s;
-webkit-transition: all 300ms ease-in-out;
transition: all 300ms ease-in-out;
}
.icon span:first-child {
top: 28px;
}
.icon span:nth-child(2) {
top: 37px;
}
.icon span:last-child {
top: 46px;
}
.icon--active span:first-child {
-webkit-transform: rotate(45deg);
-ms-transform: rotate(45deg);
transform: rotate(45deg);
position: absolute;
top: 37px;
}
.icon--active span:last-child {
-webkit-transform: rotate(-45deg);
-ms-transform: rotate(-45deg);
transform: rotate(-45deg);
position: absolute;
top: 37px;
}
.icon--active span:nth-child(2) {
opacity: 0;
}
.icon--button {
border-radius: 10px;
}
.icon-transition {
-webkit-transition: -webkit-transform 0.3s;
-webkit-transition: all 300ms ease-in-out;
transition: all 300ms ease-in-out;
}

javascript

This snippets is used to change the mobile icon to close icon on click the button. Demo