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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript 字符串</h1>
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<h2>indexOf() 方法</h2>
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<p>indexOf() 方法返回值在字符串中第一次出现的位置。</p>
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<p>查找 "welcome"：</p>
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<p id="demo"></p>
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<script>
let text = "Hello world, welcome to the universe.";
let result = text.indexOf("welcome");
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document.getElementById("demo").innerHTML = result;
</script>
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</body>
</html>
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​