JavaScript Strings
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JavaScript Strings
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JavaScript strings are used for storing and manipulating text.
JavaScript Strings
A JavaScript string is zero or more characters written inside quotes.
Example
var x = "John Doe";
Try it Yourself »
You can use single or double quotes:
Example
var carname = "Volvo XC60";
// Double quotes
var carname = '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
var answer = "It's alright";
var answer = "He is called 'Johnny'";
var answer = 'He is called "Johnny"';
Try it Yourself »
String Length
The length of a string is found in the built in property
length:
Example
var txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var sln = txt.length;Try it Yourself »
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Special Characters
Because strings must be written within quotes, JavaScript will misunderstand this string:
var x = "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
var x = "We are the so-called "Vikings" from the north.";Try it Yourself »
The sequence ' inserts a single quote in a string:
Example
var x = 'It's alright.';
Try it Yourself »
The sequence \ inserts a backslash in a string:
Example
var x = "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:
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 objectTry 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
var x = "John";
var y = new String("John");
// (x == y) is true because x and y have equal values Try it Yourself »
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)
Try it Yourself »
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
Try it Yourself »
Example
var x = new String("John");
var y = new String("John");
// (x === y) is false because x and y are different objects
Try it Yourself »
Note the difference between (x==y) and (x===y).
Comparing two JavaScript objects will always return false.
Test Yourself with Exercises!
Exercise 1 »
Exercise 2 »
Exercise 3 »
Exercise 4 »
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