HTML, CSS, JavaScript Tutorial

JavaScript Tutorial: String Variables

JavaScript strings consist of a series of consecutive characters, e.g.

var x = "Cat";

A string technically consists of a series (an ‘array’, except that a JavaScript array is a specific type of variable) of characters, which is zero-indexed. So, if we assigned x the value of "Cat" then x[0] would be "C", x[1] would be "a", etc.

Strings support the following properties and methods. Some of these involve regular expressions.

Properties:

Property	Description	More
constructor	Returns object’s constructor function	Here
length	Returns length of string	Here
prototype	Allows author to add properties and methods to an object	Here

Methods:

Method	Description	More
charAt()	Returns the character at specified index position (note strings in JavaScript are zero index based, so the first character is at position zero)	Here
charCodeAt()	Returns the Unicode character code of the character at specified index position (note strings in JavaScript are zero index based, so the first character is at position zero)	Here
concat()	Returns the result of joining two or more strings together	Here
endsWith()	Returns true if the string ends with a specified string, otherwise returns false	Here
fromCharCode()	Returns the string corresponding to a specified Unicode character	Here
includes()	Returns true if the string contains a specified string, otherwise returns false	Here
indexOf()	Returns the position of the first occurrence of a specified string in the string	Here
lastIndexOf()	Returns the position of the last occurrence of a specified string in the string	Here
localeCompare()	Returns a number which is -1 if string is before specified string in sort order, 0 if they are the same and +1 if string is after specified string in sort order	Here
match()	Searches for matches within a string versus a specified regular expression and returns these as a string array	Here
repeat()	Returns a string that repeats a specified string a specified number of times	Here
replace()	Searches for matches within a string versus a specified value (or regular expression) and returns a string in which these are replaced by another string	Here
search()	Searches for matches within a string versus a specified value or regular expression and returns the position of first occurrence of a match (or -1 if there is no match)	Here
slice()	Returns a new string formed by a part of the original string	Here
split()	Returns an array of substrings that are created by splitting the original string using a given delimiter	Here
startsWith()	Returns true if the string starts with a specified string, otherwise returns false	Here
substr()	Returns a substring defined by the start position and number of characters	Here
substring()	Returns a substring defined by the start and end position (not including the end position). If the start position is after the end position then the two are treated as reversed.	Here
toLocaleLowerCase()	Returns a string that is the original string converted to lower case characters, bearing in mind the language settings of the browser (so sometimes does not return the same as toLowerCase)	Here
toLocaleUpperCase()	Returns a string that is the original string converted to upper case characters, bearing in mind the language settings of the browser (so sometimes does not return the same as toUpperCase)	Here
toLowerCase()	Returns a string that is the original string converted to lower case characters	Here
toString()	Returns the (string) value of a string	Here
toUpperCase	Returns a string that is the original string converted to upper case characters	Here
trim()	Returns a string with whitespace (i.e. spaces) removed from start and finish of string	Here
valueOf()	Returns the primitive value of an object. For a string, this in effect just returns the string value of the string	Here

The Unicode character code returned by charCodeAt() or used as input to fromCharCode() is developed by the Unicode Consortium.

To handle special characters, you ‘escape’ the character using an escape sequence starting with a backslash character, typically followed by one of a handful of specially recognised characters (many of which were originally designed to control typewriters, so do not make much sense in HTML), or by a Unicode character of the form u followed by 4 hexadecimal characters. The following table lists a few examples of such escape sequences.

Unicode character	Alternative escape sequence (if exists)	Meaning / comment
\u005C	\\	Backslash, , i.e. \
\u0008	\b	Backspace
\u000C	\f	Form feed
\u000A	\n	Line feed (i.e. new line)
\u000D	\r	Carriage return
\u0009	\t	Horizontal tab
\u000B	\v	Vertical tab
\u0027	\'	Single quote, i.e. '
\u0022	\"	Double quote, i.e. "
\u0020		Space
\u00A0		Non-breaking space
\u2028		Line separator
\u2029		Paragraph separator

Single quotation marks do not seem to need to be escaped in a string which is delimited by double quotation marks and vice-versa, e.g. it is generally possible to define strings using e.g. the following, without needing to escape the quotation mark contained in the string.

var x = "a single quotation mark: '";

var y = 'a double quotation mark: "'

Some further quotation mark characters are included in the page on the CSS quotes property. Other types of escaping that work in other HTML or CSS contexts (or even in JavaScript regular expressions), e.g. using \005C rather than \u005C, do not necessarily work consistently or at all in JavaScript. So, for cross-browser compatibility it is usually desirable to use either the short escape sequence as above (if it exists) or a full Unicode escape sequence.

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