我们也可以在 select 元素上使用 bind:value：
App.svelte
<select
bind:value={selected}
on:change={() => answer = ''}
>注意 option 元素的值是对象，而不是字符串，不过 Svetle 并不在意。
因为我们没有给
selected设置初始值，所以绑定会自动设置一个默认值，也就是列表的第一个值。但是要注意，在绑定初始化之前，selected一直是未定义的，所以我们不能盲目地使用selected.id。（在最后的p元素中要加一个判断）
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<script>
let questions = [
{id: 1,
text: `Where did you go to school?`
},
{id: 2,
text: `What is your mother's name?`
},
{id: 3,
text: `What is another personal fact that an attacker could easily find with Google?`
}
];
let selected;
let answer = '';
function handleSubmit() {alert(
`answered question ${selected.id} (${selected.text}) with "${answer}"`);
}
</script>
<h2>Insecurity questions</h2>
<form on:submit|preventDefault={handleSubmit}><select
value={selected} on:change={() => (answer = '')}>
{#each questions as question} <option value={question}> {question.text}</option>
{/each}</select>
<input bind:value={answer} /> <button disabled={!answer} type="submit">Submit
</button>
</form>
<p>
selected question {selected? selected.id
: '[waiting...]'}
</p>