JavaScript String
JavaScript strings are used to store and process text.
JavaScript String
Strings can store a series of characters, such as "John Doe."
a string can be any character inserted into quotation marks. you can use single or double quotes:
Example
var carname = "Dodge Caliber"; var carname = 'Dodge Caliber';
you can use the index position to access each character in the string:
Example
var character = carname[7];
The index of the string starts at 0, which means that the first character index value is .0, the second is .1, and so on.
You can use quotation marks in a string, and the quotation marks in a string should not be the same as those in a string:
Example
var answer = "It's alright"; var answer = "He is called 'Johnny'"; var answer = 'He is called "Johnny"';
you can also add escape characters to strings to use quotation marks:
Example
var x = 'It\'s alright'; var y = "He is called \"Johnny\"";
The Length of The String
you can use the built-in property length to calculate the length of the string:
Example
var txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var sln = txt.length;
Special Characters
In JavaScript, strings are written in single or double quotes.
Because of this, javaScript cannot resolve the following instances:
"We are the so-called "Vikings" from the north."
The string "We are the so-called" is truncated.
How to solve the above problems? You can escape the double quotes in the "Vikings" string using the backslash, as follows:
"We are the so-called \"Vikings\" from the north."
A backslash '\' is an escape character. escape characters convert special characters to string characters:
Escaped characters can be used for escape apostrophes, line breaks, quotation marks, and other special characters.
The following table lists special characters that can be escaped in strings:
| Character | Output |
|---|---|
| \' | apostrophe |
| \" | double quotes |
| \\ | backslash |
| \n | line breaks |
| \r | enter |
| \t | tab (tab) |
| \b | the backstag |
| \f | page breaks |
A String Can be An Object
Typically, JavaScript strings are the original value and can be created using: var firstName = "Jake"
But we can also use the "new" keyword to define a string as an object: var firstName = new String("Jake")
Example
var x = "Jake";
var y = new String("Jake");
typeof x // return String
typeof y // return ObjectDo not create a String object. It slows down execution and can have other side effects:
Example
var x = "Jake";
var y = new String("Jake");
(x === y) // the result is false because x is a string and y is an object=== : It is absolutely equal, i.e. the data type and value must be equal.
String Properties and Methods
The original value string, such as "Jake," has no properties and methods (because they are not objects).
The original value can use the properties and methods of JavaScript because JavaScript can treat the original value as an object when executing methods and properties.
String methods are covered in the next section.
String Properties
| Property | Description |
|---|---|
| constructor | returns the function that created the string property |
| length | returns the length of the string |
| prototype | allows you to add properties and methods to an object |
String Methods
More examples of methods can be found in the: JavaScript String Object.
| Method | Description |
|---|---|
| charAt() | Returns the character at the specified index location |
| charCodeAt() | Returns the Unicode value of the character at the specified index location |
| concat() | Connect two or more strings and return the string after the connection |
| fromCharCode() | Convert Unicode to a string |
| indexOf() | Returns the location in the string where the specified character first appears |
| lastIndexOf() | Returns the last place in the string where the specified character appeared |
| localeCompare() | Compare the two strings in a locally specific order |
| match() | A match was found for one or more regular expressions |
| replace() | Replaces the substring that matches the regular expression |
| search() | Retrieves the value that matches the regular expression |
| slice() | Extracts fragments of the string and returns the extracted portion in the new string |
| split() | Split the string into substring arrays |
| substr() | Extracts the specified number of characters from the starting index number |
| substring() | Extracts characters between two specified index numbers in the string |
| toLocaleLowerCase() | Strings are converted to lowercase based on the host's local environment, and only a few languages, such as turkish, have locally specific case mappings |
| toLocaleUpperCase() | Strings are converted to uppercase based on the host's local environment, and only a few languages, such as turkish, have locally specific case mappings |
| toLowerCase() | Convert the string to lowercase |
| toString() | Returns the string object value |
| toUpperCase() | Convert the string to uppercase |
| trim() | Remove the left and right white space(s) of the string |
| valueOf() | Returns the original value of a string object |