在 DOM 中，每个输入值都是一个字符串。当你处理数字输入（type="number" 和 type="range"）时，这毫无用处，因为这意味着你必须记住在使用它之前强制 input.value。
¥In the DOM, every input value is a string. That’s unhelpful when you’re dealing with numeric inputs — type="number" and type="range" — as it means you have to remember to coerce input.value before using it.
使用 bind:value，Svelte 会为你处理它：
¥With bind:value, Svelte takes care of it for you:
App
<label>
<input type="number" bind:value={a} min="0" max="10" />
<input type="range" bind:value={a} min="0" max="10" />
</label>
<label>
<input type="number" bind:value={b} min="0" max="10" />
<input type="range" bind:value={b} min="0" max="10" />
</label>1
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<script>
let a = $state(1);
let b = $state(2);
</script>
<label>
<input type="number" value={a} min="0" max="10" /> <input type="range" value={a} min="0" max="10" /></label>
<label>
<input type="number" value={b} min="0" max="10" /> <input type="range" value={b} min="0" max="10" /></label>
<p>{a} + {b} = {a + b}</p>