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JavaScript Strings


JavaScript strings are used for storing and manipulating text.


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';
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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."
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The escape character (\) can also be used to insert other special characters in a string.

This is the list of 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

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

Example

document.getElementById("demo").innerHTML = "Hello \
Dolly!";
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The \ method is not a ECMAScript (JavaScript) standard.
Some browsers do not allow spaces behind the \ character.

The safest (but a little slower) way to break a long string is to use string addition:

Example

document.getElementById("demo").innerHTML = "Hello" +
"Dolly!";
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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
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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 == equality operator, equal strings look equal:

Example

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

// (x == y) is true because x and y have equal values
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When using the === equality 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)
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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
// (x == x) is true because both are the same object
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JavaScript objects cannot be compared.


Test Yourself with Exercises!

Exercise 1 »   Exercise 2 »   Exercise 3 »   Exercise 4 »