Fix watch examples (vuejs#2537)

* Add note to `watch` examples

* fix watch examples

* fix: fixed disabling an input

---------

Co-authored-by: NataliaTepluhina <[email protected]>

src/guide/essentials/watchers.md

@@ -13,7 +13,8 @@ export default {
   data() {
     return {
       question: '',
-      answer: 'Questions usually contain a question mark. ;-)'
+      answer: 'Questions usually contain a question mark. ;-)',
+      loading: false
     }
   },
   watch: {
@@ -26,12 +27,15 @@ export default {
   },
   methods: {
     async getAnswer() {
+      this.loading = true
       this.answer = 'Thinking...'
       try {
         const res = await fetch('https://yesno.wtf/api')
         this.answer = (await res.json()).answer
       } catch (error) {
         this.answer = 'Error! Could not reach the API. ' + error
+      } finally {
+        this.loading = false
       }
     }
   }
@@ -41,12 +45,12 @@ export default {
 ```vue-html
 <p>
   Ask a yes/no question:
-  <input v-model="question" />
+  <input v-model="question" :disabled="loading" />
 </p>
 <p>{{ answer }}</p>
 ```
 
-[Try it in the Playground](https://play.vuejs.org/#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)
+[Try it in the Playground](https://play.vuejs.org/#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)
 
 The `watch` option also supports a dot-delimited path as the key:
 
@@ -73,16 +77,20 @@ import { ref, watch } from 'vue'
 
 const question = ref('')
 const answer = ref('Questions usually contain a question mark. ;-)')
+const loading = ref(false)
 
 // watch works directly on a ref
 watch(question, async (newQuestion, oldQuestion) => {
-  if (newQuestion.indexOf('?') > -1) {
+  if (newQuestion.includes('?')) {
+    loading.value = true
     answer.value = 'Thinking...'
     try {
       const res = await fetch('https://yesno.wtf/api')
       answer.value = (await res.json()).answer
     } catch (error) {
       answer.value = 'Error! Could not reach the API. ' + error
+    } finally {
+      loading.value = false
     }
   }
 })
@@ -91,13 +99,13 @@ watch(question, async (newQuestion, oldQuestion) => {
 <template>
   <p>
     Ask a yes/no question:
-    <input v-model="question" />
+    <input v-model="question" :disabled="loading" />
   </p>
   <p>{{ answer }}</p>
 </template>
 ```
 
-[Try it in the Playground](https://play.vuejs.org/#eNplkkGPmzAQhf/KKxdA3Rj1mpJUUdVDT22lHrlYxDRuYOzaJjRC/PcdxyGr3b2A7PfmmzcMc3awVlxGlW2z2rdO2wCvwmj3DenBGhcww6nuCZMM7QkLOmcG5FyRN9RQa8gH/BuVD9oQdtFb5Hm5KpL8pNx6/+vu8xj9KPv+CnYFqQnyhTFIdxb4vCkjpaFb32JVnyD9lVoUpKaVVmK3x9wQoLtXgtB0VP9/cOMveYk9Np/K5MM9l7jIflScLv990nTW9EcIwXNFR3DX1YwYk4dxyrNXTlIHdCrGyk8hWL+tqqvyZMQUukpaHYOnujdtilTLHPHXGyrKUiRH8i9obx+5UM4Z98j6Pu23qH/AVzP2R5CJRMl14aRw+PldIMdH3Bh3bnzxY+FcdZW2zPvlQ1CD7WVQfALquPToP/gzL4RHqsg89rJNWq3JjgGXzWCOqt812ao3GaqEqRKHcfO8/gDLkq7r6tEyW54Bf5TTlg==)
+[Try it in the Playground](https://play.vuejs.org/#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)
 
 ### Watch Source Types {#watch-source-types}
 
@@ -253,9 +261,13 @@ The initial execution of the handler function will happen just before the `creat
 We can force a watcher's callback to be executed immediately by passing the `immediate: true` option:
 
 ```js
-watch(source, (newValue, oldValue) => {
-  // executed immediately, then again when `source` changes
-}, { immediate: true })
+watch(
+  source,
+  (newValue, oldValue) => {
+    // executed immediately, then again when `source` changes
+  },
+  { immediate: true }
+)
 ```
 
 </div>
@@ -270,12 +282,16 @@ It is common for the watcher callback to use exactly the same reactive state as
 const todoId = ref(1)
 const data = ref(null)
 
-watch(todoId, async () => {
-  const response = await fetch(
-    `https://jsonplaceholder.typicode.com/todos/${todoId.value}`
-  )
-  data.value = await response.json()
-}, { immediate: true })
+watch(
+  todoId,
+  async () => {
+    const response = await fetch(
+      `https://jsonplaceholder.typicode.com/todos/${todoId.value}`
+    )
+    data.value = await response.json()
+  },
+  { immediate: true }
+)
 ```
 
 In particular, notice how the watcher uses `todoId` twice, once as the source and then again inside the callback.