JSFiddle - React, Tailwind, and code Playground

JavaScript

var fns = {
    getName: function (fn) {
        var match = fn.toString().match(/function\s+([^\s\(]+)/);
        return match && match.length ? match[1] : match;
    },
    fn1: function () {
        return this.getName(arguments.callee);
    },
    fn2: function fn2 () {
        return this.getName(arguments.callee);
    }
}

console.log('fn1: ', fns.fn1()); // returns null
console.log('fn2: ', fns.fn2()); // returns "fn2"