JSFiddle - React, Tailwind, and code Playground

HTML

<a id="email" href="#">e-mail data</a>

JavaScript

var link = document.getElementById('email');
link.onclick = function() {
    this.href = "mailto:you@yourdomain.com?subject=Data&body=";
    this.href += getBody();
};

function getBody() {
    return 'HelloWorld';
}