JS String

JavaScript Strings

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JavaScript strings are used for storing and manipulating text.

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JavaScript Strings

A JavaScript 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 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"';

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String Length

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

Example

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

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Special Characters

Because strings must be written within quotes, JavaScript will misunderstand this string:

var y = "We are the so-called "Vikings" from the north."

The string will be chopped to "We are the so-called ".
The solution to avoid this problem, is to use the \ escape character.
The backslash escape character turns special characters into string characters:

Example

var x = 'It\'s alright';
var y = "We are the so-called \"Vikings\" from the north."

The escape character (\) can also be used to insert other special characters in a string.
These are commonly used special characters that can be inserted in a text with the backslash sign:

Code	Outputs
\'	single quote
\"	double quote
\\	backslash

Five other escape characters are valid in JavaScript:

Code	Outputs
\b	Backspace
\r	Carriage Return
\f	Form Feed
\t	Horizontal Tabulator
\v	Vertical Tabulator

The 5 escape characters above were originally designed to control typewriters, teletypes, and fax machines. They do not make any sense in HTML.

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Breaking Long Code Lines

For best readability, programmers often like to avoid code lines longer than 80 characters.
If a JavaScript statement does not fit on one line, the best place to break it is after an operator:

Example

document.getElementById("demo").innerHTML =
"Hello Dolly!";

You can also break up a code line within a text string with a single backslash:

Example

document.getElementById("demo").innerHTML = "Hello \
Dolly!";

The \ method is not the preferred method. It might not have universal support.
Some browsers do not allow spaces behind the \ character.

A safer way to break up a string, is to use string addition:

Example

document.getElementById("demo").innerHTML = "Hello" +
"Dolly!";

You cannot break up a code line with a backslash:

Example

document.getElementById("demo").innerHTML = \
"Hello Dolly!";

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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 will return string// typeof y will return object

Don't create strings as objects. It slows down execution speed.
The new keyword complicates the code. This can produce some unexpected results:

When using the == operator, equal strings are equal:

Example

var x = "John";           
var y = new String("John");

// (x == y) is true because x and y have equal values

When using the === operator, equal strings are not equal, because the === operator expects equality in both type and value.

Example

var x = "John";           
var y = new String("John");

// (x === y) is false because x and y have different types (string and object)

Or even worse. Objects cannot be compared:

Example

var x = new String("John");           
var y = new String("John");

// (x == y) is false because x and y are different objects

Example

var x = new String("John");           
var y = new String("John");

// (x === y) is false because x and y are different objects

Note the difference between (x==y) and (x===y).
Comparing two JavaScript objects will always return false.