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This time I will bring you a detailed explanation of the steps to use the JSstring method, and what are the notes when using the JS string method. The following is a practical case, let's take a look.
Return value typeObject.Method name (parameter 1[, parameter two]);
Explanation:
返回值类型：指的是函数调用结束后返回的值的类型。 对象.方法名称：指的是调用方法。 参数列表：表示函数调用时传入的参数。[]表示可选参数，可写可不写。
Definition: By a pair of "" or a pair of '' Wrapped, it is a string composed of 0 or more characters .
String length:
string.length;
eg:
var str1="abc"; var str2=""; var str3=" "; console.log(str1.length);//3 console.log(str2.length);//0 console.log(str3.length);//1
Function: This method returns the character at the corresponding position of .
Syntax: string string.charAt(index);
Parameters: index refers to 0 to string length-1 is an integer.
Return value: Returns the character at the corresponding position of the string.
Note:
- 如果传入参数小于0或者大于 字符串长度-1，则返回空字串。 - 如果传入boolean值，如果为true，默认是转化为数字1，指到字符串第二个字符。如果为false，默认是转化为数字0，指到字符串第一个字符。 - 如果传入任意字符串，则指到字符串第一个字符。
<script>
var str="abc";
console.log(str.charAt(0));//a
console.log(str.charAt(2));//c
console.log(str.charAt(-88));//""
console.log(str.charAt(false));//a
console.log(str.charAt(true));//b
console.log(str.charAt("unm"));//a
</script>
Function: Returns the Unicode value of the character corresponding to
Syntax: number string.charCodeAt(index);
Parameters: index refers to 0 to string length-1 is an integer.
Return value: Returns the Unicode value of the character at the corresponding position in the string.
Note:
If the incoming parameter is less than 0 or is greater than the string length -1, an empty string will be returned. NAN is returned.
<script>
var str="abc";
console.log(str.charCodeAt(0));//97
console.log(str.charCodeAt(2));//99
console.log(str.charCodeAt(-88));//NAN
console.log(str.charCodeAt(false));//97
console.log(str.charCodeAt(true));//98
console.log(str.charCodeAt(undefined));//97
console.log(str.charCodeAt("zzzz"));//97
</script>
Function: Convert Unicode values into corresponding characters.
Syntax: string String.fromCharCode(index);
Parameters: index refers to passing in any integer.
Return value: Returns the string corresponding to the Unicode value.
<script> console.log( String.fromCharCode( 97 ) );//a console.log( String.fromCharCode( 65 ) );//A </script>
Small example of encryption and decryption
Function: Returns the specified value string when calling this methodFirst timeThe position where it appears.
Syntax: number string.indexOf((searchValue [, fromIndex]));
Parameters: searchValue refers to The string to find. fromIndex refers to where to start searching. The default value is 0.
Return value: Returns a number.
Note: If it exists, the position will be returned, if it does not exist, -1 will be returned.
<script>
var str="abcabcabc";
console.log(str.indexOf("a"));//0
console.log(str.indexOf("b"));//1
console.log(str.indexOf("z"));//-1
console.log(str.indexOf("ab"));//0
console.log(str.indexOf("ac"));//-1
console.log(str.indexOf("bc",0));//1
console.log(str.indexOf("bc",-2));//1
console.log(str.indexOf("bc",18));//-1
</script>
Function: Returns the specified value where the last of the string appears when this method is called.
Syntax: number string.indexOf((searchValue [, fromIndex]));
Parameters: searchValue refers to The string to find. fromIndex refers to where to start searching. The default value is str.length-1.
Return value: Returns a number.
Note: If it exists, the position will be returned, if it does not exist, -1 will be returned.
<script>
var str="abcabcabc";
console.log(str.lastIndexOf("a"));//6
console.log(str.lastIndexOf("b"));//7
console.log(str.lastIndexOf("z"));//-1
console.log(str.lastIndexOf("ab"));//6
console.log(str.lastIndexOf("ac"));//-1
console.log(str.lastIndexOf("bc",0));//-1
console.log(str.lastIndexOf("bc",-2));//-1
console.log(str.lastIndexOf("bc",18));//7
</script>
Function: method extracts a part of the string and returns this new string (including the starting position, not including End position)
Syntax: string string.slice((star [, end]));
Parameters: star is Refers to the interception starting position , end refers to the interception end position , the default is position 1 of the last character (the length of the string).
Return value: Return the intercepted string.
Note:
will not exchange parameter positions according to parameter size
If there are Negative values are processed from the end. -1 refers to the last element, -2 refers to the penultimate element.
<script> var str="abcabc"; console.log(str.slice(2));//"cabc" console.log(str.slice(0,2));//"ab" console.log(str.slice(2,2));//"" console.log(str.slice(2,-1));//"cab" console.log(str.slice(2,-6));//"" console.log(str.slice(2,1));//"" console.log(str.slice(-2,-1));//"b" </script>
作用： 方法提取字符串中的一部分，并返回这个新的字符串（包含起始位置，不包含结束位置）
语法： string string.slice((star [, end]));
参数： star是指截取的起始位置，end是指截取的结束位置，默认为最后一个字符的位置+1 ( 字符串的长度 )。
返回值： 返回 截取后的字符串。
注意：
会根据起始位置和结束位置的大小先进行参数位置的变换
会把负值转换成0
<script> var str="abcabc"; console.log(str.substring(2));//"cabc" console.log(str.substring(0,2));//"ab" console.log(str.substring(2,2));//"" console.log(str.substring(2,-1));//"ab" console.log(str.substring(2,-6));//"ab" console.log(str.substring(2,1));//"b" console.log(str.substring(-2,-1));//"" </script>
作用: 截取指定 起始位置和长度 的子字符串.
语法: string string.substr(start [, length]);
参数: start :截取的起始位置 。length:截取的字符串长度，默认为字符长度。
返回值: 返回截取后的字符串
<script> var str="abcabcabcabc"; console.log(str.substr(0));//abcabcabcabc console.log(str.substr(3));//abcabcabc console.log(str.substr(3,5));//abcab console.log(str.substr(3,-1));"" </script>
1.toLowerCase
作用: 把字符串全部转成小写
语法: string string.toLowerCase();
返回值: 返回转成小写的字符串。
2.toUpperCase
作用: 把字符串全部转成大写
语法: string string.toUpperCase();
返回值: 返回转成大写的字符串。
<script> var str = "liangZhiFANG"; console.log( str.toLowerCase() );//"liangzhifang" console.log( str.toUpperCase() );//"LIANGZHIFANG" console.log( str );//"liangZhiFANG" console.log( "LoveJs".toLowerCase() );//"lovejs" </script>
作用: 通过一个指定的字符串 把原字符串分割成一个数组。
语法: array string.split([separator] [, limit])
参数:separator是指分割符。limit指定最多分割的数量，可以理解为数组长度，默认为全部。
返回值:返回一个数组。
注意:当没有分割符的时候(没有传入参数)，整个字符串将作为一个整体保存到数组中。 用分割符分割的时候，分割符会在被删除了在传入数组。
<script>
var str="我爱,你,们";
console.log(str.split(","));//["我爱","你","们"]
console.log(str.split(",",2));//["我爱","你"]
console.log(str.split());//["我爱,你,们"]
console.log(str.split("mmm"));//["我爱,你,们"]
console.log(str.split(""));//["我", "爱", "," , "你", "," ,"们"]
</script>
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