JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="content">
        <div class="line-1">Line 1</div>
        <div class="line-2">Line 2</div>
        <div class="line-3">Line 3</div>
        <div class="line-4">Line 4</div>
        <div class="line-5">Line 5</div>
        <div class="line-6">Line 6</div>
        <div class="line-7">Line 7</div>
        <div class="line-8">Line 8</div>
        <div class="line-9">Line 9</div>
    </div>
    <div class="buttons">
    </div>
</div>
<div class="container">
    <div class="content">
        <div class="line-1">Line 1</div>
        <div class="line-2">Line 2</div>
        <div class="line-3">Line 3</div>
        <div class="line-4">Line 4</div>
        <div class="line-5">Line 5</div>
        <div class="line-6">Line 6</div>
    </div>
    <div class="buttons">
    </div>
</div>

CSS

.container
    {
        margin-bottom: 20px;
    }

.content
    {
        overflow: hidden;
        height: 100px;
        padding: 10px;
        border: 1px solid #ccc;
    }

JavaScript

if ((".content").offsetHeight < (".content").scrollHeight)
    {
        $( ".container .buttons" ).append( "<button>Up</button><button>Down</button>" );
    }