submit form ToDo examples and docs

Author: tonyspiro

docs/basics/ExampleTodoList.md

@@ -347,15 +347,21 @@ let AddTodo = ({ dispatch }) => {
 
   return (
     <div>
-      <input ref={node => {
-        input = node
-      }} />
-      <button onClick={() => {
+      <form onSubmit={e => {
+        e.preventDefault()
+        if (!input.value.trim()) {
+          return
+        }
         dispatch(addTodo(input.value))
         input.value = ''
       }}>
-        Add Todo
-      </button>
+        <input ref={node => {
+          input = node
+        }} />
+        <button type="submit">
+          Add Todo
+        </button>
+      </form>
     </div>
   )
 }

examples/todos-with-undo/containers/AddTodo.js

@@ -9,9 +9,10 @@ let AddTodo = ({ dispatch }) => {
     <div>
       <form onSubmit={e => {
         e.preventDefault()
-        if (input.value.trim()) {
-          dispatch(addTodo(input.value))
+        if (!input.value.trim()) {
+          return
         }
+        dispatch(addTodo(input.value))
         input.value = ''
       }}>
         <input ref={node => {

examples/todos/containers/AddTodo.js

@@ -9,9 +9,10 @@ let AddTodo = ({ dispatch }) => {
     <div>
       <form onSubmit={e => {
         e.preventDefault()
-        if (input.value.trim()) {
-          dispatch(addTodo(input.value))
+        if (!input.value.trim()) {
+          return
         }
+        dispatch(addTodo(input.value))
         input.value = ''
       }}>
         <input ref={node => {