JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://unpkg.com/handlebars@latest/dist/handlebars.js"></script>
<!-- 
If you need a specific version:
<script src="https://unpkg.com/handlebars@4.3.0/dist/handlebars.js"></script> -->

<div id="output"></div>
<script type="template/handlebars" id="template">{{aString.trim}}</script>

JavaScript

var template;

template = Handlebars.compile(document.getElementById('template').innerHTML);

const result = template(
  { aString: "  abc  " },
  {
    allowedProtoMethods: {
      trim: true
    }
  }
);

console.log(result, typeof result);

document.getElementById('output').innerHTML = result;