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
let carName1 = "Volvo XC60";
// Double quotes
let carName2 = '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
let answer1 = "It's alright";
let answer2 = "He is called 'Johnny'";
let answer3 = 'He is called "Johnny"';
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String Length
To find the length of a string, use the built-in length property:
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:
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:
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
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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
let x = "John";
let y = new String("John");
// (x == y) is true because x and y have equal values
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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)
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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
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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.
