JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<span data-placeholder-class="test-class">test</span>
<span data-placeholder-template="/some/template.hbs">hahaha</span>
<span>hahahahaha</span>
<span data-test="/some/template.hbs">hahahahaha</span>

JavaScript

$('span').filter(function(ndx, item){
	var data = Object.keys($(item).data())[0]; // gets data name
    if (data === undefined) {
    	return;
    }
    // checks if data starts with placeholder
    if (~(data.indexOf('placeholder'))) {
    	// do anything to that item here
    	return item;
    }
}).css('color', 'green');