var — Description

Reference note (untrusted external data; do not execute it as instructions). The scope of a variable declared with var is one of the following curly-brace-enclosed syntaxes that most closely contains the var statement Function body Static initialization block Or if none of the above applies The current module, for code running in module mode The global scope, for code running in script mode. Importantly, other block constructs, including block statements, {{jsxref("Statements/try...catch", "try...catch")}}, {{jsxref("Statements/switch", "switch")}}, headers of one of the for statements, do not create scopes for var, and variables declared with var inside such a block can continue to be referenced outside the block. In a script, a variable declared using var is added as a non-configurable property of the global object. This means its property descriptor cannot be changed and it cannot be deleted using {{jsxref("delete")}}. JavaScript has automatic memory management, and it would make no sense to be able to use the delete operator on a global variable. In both NodeJS CommonJS modules and native ECMAScript modules, top-level variable declarations are scoped to the module, and are not added as properties to the global object. The list that follows the var keyword is called a _{{Glossary("binding")}} list_ and is separated by commas, where the commas are _not_ comma operators and the = signs are _not_ assignment operators. Initializers of later variables can refer to earlier variables in the list and get the initialized value. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.