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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript 数字</h1>
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<h2>toPrecision() 方法</h2>
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<p>toPrecision() 将数字格式化为指定长度：</p>
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<p id="demo"></p>
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<script>
let num = 0.001658853;
let n = num.toPrecision();
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document.getElementById("demo").innerHTML = n;
</script>
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</body>
</html>
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