JSFiddle - React, Tailwind, and code Playground

JavaScript

Function.prototype.getBody =
  function() {
    // Get content between first { and last }
    var m = this.toString().match(/\{([\s\S]*)\}/m)[1];
    // Strip comments
    return m.replace(/^\s*\/\/.*$/mg,'');
  };

function foo() {
    var a = 1, b = "bar";
    alert(b + a);
    return null;
}

console.log(foo.getBody());
console.log(foo.getBody().length);