If you're interesting in a reactive template library that doesn't require a compiler for non-standard JavaScript syntax, check out a library I've been working on for a little while now, lit-html: https://github.com/Polymer/lit-html

Where JSX would look like this:

    const view = (state, actions) => (
      <div>
        <h1>{state.count}</h1>
        <button onclick={() => actions.down(1)}>-</button>
        <button onclick={() => actions.up(1)}>+</button>
      </div>
    )

The lit-html would be:

    const view = (state, actions) => html`
      <div>
        <h1>{state.count}</h1>
        <button onclick={() => actions.down(1)}>-</button>
        <button onclick={() => actions.up(1)}>+</button>
      </div>
    `;

Nearly identical. lit-html uses `<template>`s and cloning, so that it doesn't have to do any expensive VDOM diffs.