1. Properties:
To determine the length of a string, use the string's length property. For example, to get the length of the string s:
s.length
2. Method:
In addition to the length property, strings also provide many methods to call:
var s = "hello, world";
s.charAt(0); //"h": the first character. Equivalent to s[0]
s.charAt(s.length-1); //"d": the last character. Equivalent to s[s.length-1]
s.substring(1,4); //"ell": 2~4 characters
s.slice(1,4); //"ell": same as above
s.slice(-4); //"orld": the last four characters
s.indexOf("l"); //2: The position where the character l first appears
s.lastIndexOf("l"); //10: The position of the last occurrence of the character l
s.indexOf("l",3); //3: The position where the character l appears for the first time in position 3 and later
s.splite(", "); //["hello","world"] split into substrings
s.replace("h","H"); //"Hello, world": full text string replacement
s.toUppercase() //"HELLO, WORLD"