chartAt(索引)，返回索引对应字符
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<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>// chartAt(索引)，返回索引对应字符var str = "xiaoming"var str1 = str.charAt(0)console.log(str,str1)</script>
</body>
</html>
chartCodeAt(索引)，返回索引对应的ascii编码
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<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>var str = "xiaoming"// chartCodeAt(索引)，返回索引对应的ascii编码var str1 = str.charCodeAt(0)console.log(str1)</script>
</body>
</html>
toUpperCase()小写转大写 toLowerCase()大写转小写
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<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>var str = "xiaoming"var str1 = "XIAOMING"// toUpperCase()小写转大写console.log(str.toUpperCase())// toLowerCase()大写转小写console.log(str1.toLowerCase())</script>
</body>
</html>
substr和substring
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<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
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<body><script>//截取 substr(开始索引，长度) substring(开始索引，结束索引) slicevar str1 = str.substr(0,2)var str2 = str.substring(1,2)var str3 = str.substring(1)var str4 = str.slice(1,2)var str5 = str.slice(1)console.log(str1)console.log(str2)console.log(str3)console.log(str4)console.log(str5)</script>
</body>
</html> 
replace替换
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<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>var str = "xiaoming"// replace只替换第一个var str1 = str.replace("i","*")console.log(str1)</script>
</body>
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