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来源：3-16 编程练习

昏睡红茶厘米

2020-11-16 22:30:22

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>toUpperCase和toLowerCase</title>
</head>
<body>
<script>
    var str="Never deter till tomorrow that which you can do today";
    var word = "tomorrow";
    var index=str.indexOf(word);
    var strNew=str.substr(index,word.length);
    var upperStr=strNew.toUpperCase();
    console.log(str)
    console.log(upperStr)
    var str_1 = str.substring(0,index)
    var str_2 = str.substring(index+word.length)
    document.write(str_1+upperStr+str_2);
</script>
</body>
</html>