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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript 数组方法</h1> 
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<h2>unshift()</h2>
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<p>unshift() 方法将新元素添加到数组的开头。</p>
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<button onclick="myFunction()">试一试</button>
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<p id="demo"></p>
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<script>
var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits;
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function myFunction() {
  fruits.unshift("Lemon");
  document.getElementById("demo").innerHTML = fruits;
}
</script>
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</body>
</html>
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