Improve demo (#136)

* demo: evaluate on input instead of on button press

* demo: use `monospace` font

* demo: make the input blank initially (remove space)

index.html

@@ -28,6 +28,7 @@
 
   .demo__repl {
     display: flex;
+    font-family: monospace;
   }
 
   .output {
@@ -64,7 +65,6 @@
       <textarea class="form-control textbox"></textarea>
       <p class="output"></p>
     </div>
-    <button type="buttont" class="btn btn-primary">Evaluate</button>
   </div>
 </body>
 

index.js

@@ -6,12 +6,12 @@ const rust = import("./pkg");
 
 rust.then(m => {
   window.evaluate = m.evaluate;
-  let button = document.querySelector("button");
+  let textarea = document.querySelector("textarea");
-  button.addEventListener("click", clickHandler);
+  textarea.addEventListener("input", inputHandler);
 });
 
-function clickHandler(evt) {
+function inputHandler(evt) {
-  let text = document.querySelector("textarea").value;
+  let text = evt.target.value;
   let p = document.querySelector("p.output");
   let t0 = performance.now();
   let result = window.evaluate(text);