JSFiddle - React, Tailwind, and code Playground

HTML

<div class="span3"> 
<input type="text" name="nama_kelas" value="Nama Kelas" style="width: 200px" class="input-block-level" onfocus="bersihkan(this)" onblur="kembali_semula(this)"/>
    </div>
    <div class="span3"> 
        <span id="simpan_kelas" onclick="simpan_kelas(this)" class="btn btn-success"><i class="icon-plus icon-white"></i> Kelas</span>
        <span id="update_kelas" style="display:none">
        </span>

JavaScript

function simpan_kelas(elm){
    var nama_kelas = $(elm).prev().val();
    if(nama_kelas != "" && nama_kelas != "nama_kelas"){
        //simpan ke database

        var data = $("[name='nama_kelas']").val();
        alert(data)
 }
 }