computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includin ...

, a literal is a notation for representing a fixed value in

source code In computing, source code, or simply code, is any collection of code, with or without comment (computer programming), comments, written using a human-readable programming language, usually as plain text. The source code of a Computer program, p ...

. Almost all programming languages have notations for atomic values such as

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...

s, floating-point numbers, and

string String or strings may refer to: *String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects Arts, entertainment, and media Films * ''Strings'' (1991 film), a Canadian anim ...

s, and usually for booleans and

characters Character or Characters may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to The ...

; some also have notations for elements of enumerated types and compound values such as arrays,

record A record, recording or records may refer to: An item or collection of data Computing * Record (computer science), a data structure ** Record, or row (database), a set of fields in a database related to one entity ** Boot sector or boot record, ...

s, and objects. An

anonymous function In computer programming, an anonymous function (function literal, lambda abstraction, lambda function, lambda expression or block) is a function definition that is not bound to an identifier. Anonymous functions are often arguments being passed t ...

is a literal for the

function type In computer science and mathematical logic, a function type (or arrow type or exponential) is the type of a variable or parameter to which a function has or can be assigned, or an argument or result type of a higher-order function taking or ret ...

. In contrast to literals, variables or constants are symbols that can take on one of a class of fixed values, the constant being constrained not to change. Literals are often used to initialize variables; for example, in the following, 1 is an integer literal and the three letter string in "cat" is a string literal: int a = 1; string s = "cat"; In

lexical analysis In computer science, lexical analysis, lexing or tokenization is the process of converting a sequence of characters (such as in a computer program or web page) into a sequence of ''lexical tokens'' ( strings with an assigned and thus identified ...

, literals of a given type are generally a token type, with a grammar rule, like "a string of digits" for an integer literal. Some literals are specific

keywords Keyword may refer to: Computing * Keyword (Internet search), a word or phrase typically used by bloggers or online content creator to rank a web page on a particular topic * Index term, a term used as a keyword to documents in an information syste ...

, like true for the boolean literal "true". In some object-oriented languages (like

ECMAScript ECMAScript (; ES) is a JavaScript standard intended to ensure the interoperability of web pages across different browsers. It is standardized by Ecma International in the documenECMA-262 ECMAScript is commonly used for client-side scriptin ...

), objects can also be represented by literals. Methods of this object can be specified in the object literal using function literals. The brace notation below, which is also used for array literals, is typical for object literals:

Literals of objects

(as well as its implementations

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of Website, websites use JavaScript on the Client (computing), client side ...

ActionScript ActionScript is an object-oriented programming language originally developed by Macromedia Inc. (later acquired by Adobe). It is influenced by HyperTalk, the scripting language for HyperCard. It is now an implementation of ECMAScript (meani ...

), an object with methods can be written using the object literal like this: var newobj = ; newobj.method1(); newobj.method2(); These object literals are similar to anonymous classes in other languages like

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...

. The

JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other s ...

data interchange format is based on a subset of the JavaScript object literal syntax, with some additional restrictions (among them requiring all keys to be quoted, and disallowing functions and everything else except data literals). Because of this, ''almost'' every valid JSON document (except for some subtleties with escaping) is also valid JavaScript code, a fact exploited in the JSONP technique.

References

{{DEFAULTSORT:Literal (Computer Science) Programming constructs

Literals of objects

See also

References