一、基礎

v-model 指令在表單<input>、<textarea>及<select>元素上建立雙向資料繫結

1.文字

    <div id="vm">
        <input v-model="message" placeholder="edit me" />
        <p>Message is: {{ message }}</p>
    </div>
    <script>
        const v = Vue.createApp({
            data() {
                
 
return {
                    message:null
                }
            }
        }).mount('#vm')
    </script>

2.多行文字

        <p style="white-space: pre-line;">{{ message }}</p>
        <br>
        <textarea v-model="message" ></textarea>

文字區域插值不起作用，應該使用v-model來代替

3.複選框

    <div id="vm">
        <input type="checkbox" id="jack" value="Jack" v-model="checkedNames">
        <label for="jack">Jack</label>
        <input type="checkbox" id="john" value="John" v-model="checkedNames">
        <label for="john">John</label>
        <
 
input type="checkbox" id="mike" value="Mike" v-model="checkedNames">
        <label for="mike">Mike</label>
        <br>
        <span>Checked names: {{ checkedNames }}</span>
    </div>
    <script>
        const v = Vue.createApp({
            data() {
                return {
                    checkedNames: []
                }
            }
        }).mount('#vm')
    </script>

4.單選按鈕

    <div id="vm">
        <input type="radio" id="one" value="One" v-model="picked">
        <label for="one">One</label>
        <br>
        <input type="radio" id="two" value="Two" v-model="picked">
        <label for="two">Two</label>
        <br>
        <span>Picked: {{ picked }}</span>
    </div>
    <script>
        const v = Vue.createApp({
            data() {
                return {
                    picked: ''
                }
            }
        }).mount('#vm')
    </script>

5.選擇框

（1）簡單

   <div id="vm">
        <select v-model="selected">
            <option disabled value="">請選擇</option>
            <option>A</option>
            <option>B</option>
            <option>C</option>
        </select>
        <span>Selected: {{ selected }}</span>
    </div>
    <script>
        const v = Vue.createApp({
            data() {
                return {
                    selected: ''
                }
            }
        }).mount('#vm')
    </script>

（2）多選

    <div id="vm">
        <select v-model="selected" multiple style="width: 50px;">
            <option>A</option>
            <option>B</option>
            <option>C</option>
        </select>
        <br>
        <span>Selected: {{ selected }}</span>
    </div>
    <script>
        const v = Vue.createApp({
            data() {
                return {
                    selected: []
                }
            }
        }).mount('#vm')
    </script>

（3）v-for動態渲染

    <div id="vm">
        <select v-model="selected">
            <option v-for="option in options" v-bind:value="option.value">
                {{ option.text }}
            </option>
        </select>
        <span>Selected: {{ selected }}</span>
    </div>
    <script>
        const v = Vue.createApp({
            data() {
                return {
                    selected: 'A',
                    options: [
                        { text: 'One', value: 'A' },
                        { text: 'Two', value: 'B' },
                        { text: 'Three', value: 'C' }
                    ]
                }
            }
        }).mount('#vm')
    </script>

二、值繫結