JavaScript Strings
JavaScript strings are used for storing and manipulating text.
JavaScript Strings
A JavaScript string is zero or more characters written inside quotes.
You can use single or double quotes:
Example
var carname = "Volvo XC60";
// Double quotes
var carname = 'Volvo XC60'; // Single quotes
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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:
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:
The sequence \' inserts a single quote in a string:
The sequence \\ inserts a backslash in a string:
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:
You can also break up a code line within a text string with a single backslash:
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:
You cannot break up a code line with a backslash:
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 == 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
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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)
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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
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Example
var x = new String("John");
var y = new String("John");
// (x === y) is false because x and y are different objects
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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 »
