String & Methods

JavaScript strings are used for storing and manipulating text.


JavaScript Strings

A string simply stores a series of characters like "John Doe".

A string can be any text inside quotes. You can use single or double quotes:

Example

var
carname = "Volvo XC60";
var
carname = ‘Volvo XC60’;

You can access each character in a string with its position (index):

Example

var character = carname[7];

String indexes are zero-based, which means the first character is [0], the
second is [1], and so on.

You can use quotes inside a string, as long as they don’t match the quotes
surrounding the string:

Example

var answer = "It’s alright";
var answer = "He is called ‘Johnny’";
var answer = ‘He is called "Johnny"’;

Or you can put quotes inside a string by using the \ escape character:

Example

var answer = ‘It\’s alright’;
var answer = "He is called \"Johnny\"";


String Length

The length of a string (a string object) is found in the built in property
length:

Example

var txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var sln = txt.length;


Special Characters

In JavaScript, strings are written as characters inside single or double quotes.

Because of this, JavaScript will misunderstand this string:

 "We are the so-called "Vikings" from the north."

The string will be chopped to "We are the so-called ".

To solve this problem, you can place a backslash (\) before the double quotes in "Vikings":

 "We are the so-called \"Vikings\" from the north."

 The backslash is an escape character. Escape
characters turns special characters into string characters:

The escape character (\) can be used to insert apostrophes, new lines, quotes, and other special characters into a string.

The table below lists other special characters that can be added to a text string with the backslash sign:

Code Outputs
\’ single quote
\" double quote
\\ backslash
\n new line
\r carriage return
\t tab
\b backspace
\f form feed


Strings Can be Objects

Normally, JavaScript strings are primitive values, created from literals:
var firstName = "John"

But strings can also be defined as objects with the keyword new: var
firstName = new
String("John")

Example

var x = "John";
var y = new String("John");
typeof x // returns String
typeof y // returns Object

Don’t create String objects.
They slow down execution speed, and produce nasty side effects:

Example

var x = "John";             
var y = new String("John");
(x === y) // is false because x is a string and y is an object.


String Properties and Methods

Primitive values, like "John", cannot have properties
or methods (because they are not objects).

But with JavaScript, methods and properties are also available to
primitive values, because JavaScript treats primitive values
as objects when executing methods and properties.

String methods are covered in next chapter.


String Properties

Property Description
constructor Returns the function that created the String object’s prototype
length Returns the length of a string
prototype Allows you to add properties and methods to an object


String Methods

Method Description
charAt() Returns the character at the specified index
charCodeAt() Returns the Unicode of the character at the specified
index
concat() Joins two or more strings, and returns a copy of the joined strings
fromCharCode() Converts Unicode values to characters
indexOf() Returns the position of the first found occurrence of a specified value in a string
lastIndexOf() Returns the position of the last found occurrence of a specified value
in a string
localeCompare() Compares two strings in the current locale
match() Searches a string for a match against a regular expression, and returns
the matches
replace() Searches a string for a value and
returns a new string with the value replaced
search() Searches a string for a and
returns the position of the match
slice() Extracts a part of a string and returns a new string
split() Splits a string into an array of substrings
substr() Extracts a part of a string from a start
position through a number of characters
substring() Extracts a part of a string between two specified positions
toLocaleLowerCase() Converts a string to lowercase letters, according to the host’s locale
toLocaleUpperCase() Converts a string to uppercase letters, according to the host’s locale
toLowerCase() Converts a string to lowercase letters
toString() Returns the value of a String object
toUpperCase() Converts a string to uppercase letters
trim() Removes whitespace from both ends of a string
valueOf() Returns the primitive value of a String object

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