Enabled multiline input to easily paste several lines from an external editor. Sth like backslash in bash doesn't work; don't see the need for that

src/app.css

@@ -61,12 +61,25 @@ svg {
     bottom: 0;
 }
 
-#command_input{
+.multiline{
+    border-top: 1px slategray solid;
+    border-left: 1px slategray solid;
+    border-right: 1px slategray solid;
+    border-bottom: none transparent;
+    border-top-left-radius: 3px;
+    border-top-right-radius: 3px;
+}
+
+.single_line{
     border: none transparent;
-    background: black;
+}
+
+#command_input{
+    background: #111;
     color: greenyellow;
     outline: none;
     width: 39vw;
+    height: 1em;
 }
 
 #command_history{

src/console.js

@@ -6,10 +6,21 @@
         const command_input_element = document.getElementById('command_input');
         const command_history_element = document.getElementById('command_history');
         command_input_element.value = '';
-        let command_history = [];
+        let command_history = [''];
         let command_history_index = 0;
 
+        let adjust_input_element_height = function(){
+            let num_lines=command_input_element.value.split(/\n/).length;
+            command_input_element.setAttribute('style', 'height: ' + num_lines + 'em');
+            if (num_lines>1){
+                command_input_element.setAttribute('class','multiline');
+            } else {
+                command_input_element.setAttribute('class','single_line');
+            }
+        }
+
         command_input_element.onkeyup = function handle_key_input(event) {
+            adjust_input_element_height();
             if (event.key === 'ArrowUp') {
                 if (command_history_index > -1) {
                     command_input_element.value = command_history[command_history_index];
@@ -27,7 +38,13 @@
                 }
             }
             if (event.key === 'Enter') {
-                let command = command_input_element.value;
+                let commands = command_input_element.value;
+                command_input_element.value='';
+                adjust_input_element_height();
+                let command_array = commands.split(/\n/);
+                for (let i = 0; i < command_array.length; i++) {
+                    let command = command_array[i];
+                    if (command.length > 0) {
                         command_history_element.innerText += command + "\n";
                         command_input_element.value = '';
                         command_history_index = command_history.length;
@@ -46,6 +63,8 @@
                         command_history.push(command);
                         command_history_element.scrollTo(0, command_history_element.scrollHeight);
                     }
+                }
+            }
         };
 
         let visit_expression = function (expr) {

src/index.html

@@ -9,7 +9,7 @@
 <div id="console">
     <div id="command_history"><div id="bottom"></div></div>
     <label id="prompt">&gt;
-        <input id="command_input" type="text" autofocus/>
+        <textarea id="command_input" class="single_line" autofocus></textarea>
     </label>
 </div>
 <script type="application/ecmascript" src="index.js"></script>