JSFiddle - React, Tailwind, and code Playground

by tea4two

HTML

<form action="">
  <input type="text" id="test">
  <button>送信</button>
</form>

JavaScript

var input = document.querySelector('#test');

if( input.value !== '' && input.value.length >= 5 ) {
	alert('空です');
} else {
	alert('空ではありません');
}


var pref = ['北海道','東京','大阪','沖縄'];
var list = '';

pref.forEach(function(data, i){
		list += '<li>' + data + '</li>';
});

document.body.innerHTML = list;