JSFiddle - React, Tailwind, and code Playground

HTML

<div class="skill-bar">
    <span></span>
</div>

CSS

.skill-bar {
    width: 57%;
    float: left;
    height: 11px;
    border-radius: 5px;
    position: relative;
    margin: 6px 0 12px 0;
    border: 2px solid #00edc2;
}
.skill-bar span {
    background: #00edc2;
    height: 7px;
    border-radius: 5px;
    display: inline-block;
    width: 0;
    transition: width 1s ease;
    -webkit-transition: width 1s ease;
    background-color: #00edc2;
}
.skill-bar span.w70 {
    width: 70%;
}

JavaScript

$(".skill-bar span").addClass("w70");