Compare JS's substring, substr, and C # substring

The role of JS Substring and C # substring is to intercept a substring from a string, but there are a lot of different ways to use them, so let's look at the following:
JS's substring
Grammar:

Program code string.substring (Start, end)

Description: Returns a substring from start to end that does not contain end.
Example:

Program code var str= "ABCDEFGH"; document.write (str.substring (0,1));//return:a document.write (str.substring (2,5));//return:cde document.write ( Str.substring (7,8));//return:h

substring in C #
Grammar:

Program code string.substring (int startIndex) string.substring (int startIndex, int length)

Description: Returns a substring starting from startindex to the end, or a substring that starts at startindex and length.
Example:

program code String str = "ABCDEFGH"; Response.Write (str. Substring (0,1));//return:a Response.Write (str. Substring (2,3));//return:cde Response.Write (str. Substring (7,1));//return:h Response.Write (str. Substring (7));//return:h Response.Write (str. Substring);//error:startindex cannot be greater than the string length. Response.Write (str. Substring (7,10));//error: The index and length must refer to the position within the string.

After the above instructions on their use should have a relatively clear understanding, but the JS substring still have a few points to explain:
1.start is not necessarily the first parameter, end is not necessarily the second parameter, substring (3,1), the starting position is 1, the end position is 3; 2. When the substring to be returned is from the start position to the end, The value of end must be greater than the length of the string (that is, the index greater than or equal to the string), such as the top of str.substring (7,8), according to the index from 0 to calculate the end of the maximum value is 7, but this is 8, of course, the use of more than 8 of the results returned is the same, this is more

JS's substr

Grammar:

Program code STRINGOBJECT.SUBSTR (start,length) Description: Extracts a specified number of characters from the start subscript in a string. Start Required. The starting subscript for the substring to extract. Must be numeric. If it is a negative number, the argument declares the position from the end of the string. That is,-1 refers to the last character in the string, 2 refers to the second-lowest character, and so on. Length is optional. The number of characters in the substring. Must be numeric. If this argument is omitted, then the string from the beginning of the stringobject to the end is returned. Example: Program code

<script type= "Text/javascript" > var str= "Hello world!" document.write (STR.SUBSTR (3)) </script>

Output:

Lo world!

Compare JS's substring, substr, and C # substring