how to custom select element css code example

Example 1: how to add a selection in css

.custom-select-wrapper {
     position: relative;
     user-select: none;
     width: 100%;
}
 .custom-select {
     position: relative;
     display: flex;
     flex-direction: column;
     border-width: 0 2px 0 2px;
     border-style: solid;
     border-color: #394a6d;
}
 .custom-select__trigger {
     position: relative;
     display: flex;
     align-items: center;
     justify-content: space-between;
     padding: 0 22px;
     font-size: 20px;
     font-weight: 300;
     color: #3b3b3b;
     height: 60px;
     line-height: 60px;
     background: #ffffff;
     cursor: pointer;
     border-width: 2px 0 2px 0;
     border-style: solid;
     border-color: #394a6d;
}
 .custom-options {
     position: absolute;
     display: block;
     top: 100%;
     left: 0;
     right: 0;
     border: 2px solid #394a6d;
     border-top: 0;
     background: #fff;
     transition: all 0.5s;
     opacity: 0;
     visibility: hidden;
     pointer-events: none;
     z-index: 2;
}
 .custom-select.open .custom-options {
     opacity: 1;
     visibility: visible;
     pointer-events: all;
}
 .custom-option {
     position: relative;
     display: block;
     padding: 0 22px 0 22px;
     font-size: 22px;
     font-weight: 300;
     color: #3b3b3b;
     line-height: 60px;
     cursor: pointer;
     transition: all 0.5s;
}
 .custom-option:hover {
     cursor: pointer;
     background-color: #b2b2b2;
}
 .custom-option.selected {
     color: #ffffff;
     background-color: #305c91;
}

Example 2: how to add a selection in css

/* http://meyerweb.com/eric/tools/css/reset/ v2.0 | 20110126 License: none (public domain) */
 html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video {
     margin: 0;
     padding: 0;
     border: 0;
     font-size: 100%;
     font: inherit;
     vertical-align: baseline;
}
/* HTML5 display-role reset for older browsers */
 article, aside, details, figcaption, figure, footer, header, hgroup, menu, nav, section {
     display: block;
}
 body {
     line-height: 1;
}
 ol, ul {
     list-style: none;
}
 blockquote, q {
     quotes: none;
}
 blockquote:before, blockquote:after, q:before, q:after {
     content: '';
     content: none;
}
 table {
     border-collapse: collapse;
     border-spacing: 0;
}