JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
    <input placeholder="Search items..."/>
    <button>Search</button>
</div>

CSS

.wrapper {
    position: relative;
    width: 75%;
}

input {
    float: left;
    box-sizing: border-box;
    padding-right: 80px;
    width: 100%;
}

button {
    position: absolute;
    top: 0;
    right: 0;
    width: 80px;
}