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JavaScript Strings


JavaScript strings are used for storing and manipulating text.


JavaScript Strings

A JavaScript string is zero or more characters written inside quotes.

Example

let text = "John Doe";
Try it Yourself »

You can use single or double quotes:

Example

let carName1 = "Volvo XC60";  // Double quotes
let carName2 = 'Volvo XC60';  // Single quotes
Try it Yourself »

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

Example

let answer1 = "It's alright";
let answer2 = "He is called 'Johnny'";
let answer3 = 'He is called "Johnny"';
Try it Yourself »

String Length

To find the length of a string, use the built-in length property:

Example

let text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
text.length;    // Will return 26
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Escape Character

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

let text = "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 backslash escape character.

The backslash (\) escape character turns special characters into string characters:

Code Result Description
\' ' Single quote
\" " Double quote
\\ \ Backslash

The sequence \"  inserts a double quote in a string:

Example

let text = "We are the so-called \"Vikings\" from the north.";
Try it Yourself »

The sequence \'  inserts a single quote in a string:

Example

let text= 'It\'s alright.';
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The sequence \\  inserts a backslash in a string:

Example

let text = "The character \\ is called backslash.";
Try it Yourself »

Six other escape sequences are valid in JavaScript:

Code Result
\b Backspace
\f Form Feed
\n New Line
\r Carriage Return
\t Horizontal Tabulator
\v Vertical Tabulator

The 6 escape characters above were originally designed to control typewriters, teletypes, and fax machines. They do not make any sense in HTML.


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!";
Try it Yourself »

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

Example

document.getElementById("demo").innerHTML = "Hello \
Dolly!";
Try it Yourself »

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!";
Try it Yourself »

You cannot break up a code line with a backslash:

Example

document.getElementById("demo").innerHTML = \
"Hello Dolly!";
Try it Yourself »

Strings Can be Objects

Normally, JavaScript strings are primitive values, created from literals:

let firstName = "John";

But strings can also be defined as objects with the keyword new:

let firstName = new String("John");

Example

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

// typeof x will return string
// typeof y will return object
Try it Yourself »

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

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

// (x == y) is true because x and y have equal values
Try it Yourself »

When using the === operator, equal values may not be equal, because the === operator expects equality in both data type and value.

Example

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

// (x === y) is false because x and y have different types (string and object)
Try it Yourself »

Or even worse. Objects cannot be compared:

Example

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

// (x == y) is false because x and y are objects
Try it Yourself »

Example

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

// (x === y) is false because x and y are objects
Try it Yourself »

Note the difference between (x==y) and (x===y).
Also note that comparing two JavaScript objects will always return false.