This page lists features of JavaScript that are deprecated (that is, still available but planned for removal) and obsolete (that is, no longer usable).
Deprecated features
These deprecated features can still be used, but should be used with caution because they are expected to be removed entirely sometime in the future. You should work to remove their use from your code.
RegExp properties
The following properties are deprecated. This does not affect their use in {{jsxref("Global_Objects/String/replace", "replacement strings", "", 1)}}:
Property | Description |
---|---|
$1, ..., $9 |
Parenthesized substring matches, if any. |
$_ |
See input . |
$* |
See multiline . |
$& |
See lastMatch . |
$+ |
See lastParen . |
$` |
See leftContext . |
$' |
See rightContext . |
input |
The string against which a regular expression is matched. |
lastMatch |
The last matched characters. |
lastParen |
The last parenthesized substring match, if any. |
leftContext |
The substring preceding the most recent match. |
rightContext |
The substring following the most recent match. |
The following are now properties of RegExp instances, no longer of the RegExp object:
Property | Description |
---|---|
global |
Whether or not to test the regular expression against all possible matches in a string, or only against the first. |
ignoreCase |
Whether or not to ignore case while attempting a match in a string. |
lastIndex |
The index at which to start the next match. |
multiline |
Whether or not to search in strings across multiple lines. |
source |
The text of the pattern. |
RegExp methods
- The
compile
method is deprecated. - The
valueOf
method is no longer specialized for RegExp. UseObject.valueOf
.
Function properties
- The {{jsxref("Global_Objects/Function/caller", "caller")}} and {{jsxref("Global_Objects/Function/arguments", "arguments")}} properties are deprecated, because they leak the function caller. Instead of the arguments property, you should use the {{jsxref("Functions/arguments", "arguments")}} object inside function closures.
Legacy generator
- {{jsxref("Statements/Legacy_generator_function", "Legacy generator function statement")}} and {{jsxref("Operators/Legacy_generator_function", "Legacy generator function expression")}} are deprecated. Use {{jsxref("Statements/function*", "function* statement")}} and {{jsxref("Operators/function*", "function* expression")}} instead.
- {{jsxref("Operators/Array_comprehensions", "JS1.7/JS1.8 Array comprehension", "#Differences_to_the_older_JS1.7.2FJS1.8_comprehensions")}} and {{jsxref("Operators/Generator_comprehensions", "JS1.7/JS1.8 Generator comprehension", "#Differences_to_the_older_JS1.7.2FJS1.8_comprehensions")}} are deprecated.
Iterator
- {{jsxref("Global_Objects/StopIteration", "StopIteration")}} is deprecated.
- {{jsxref("Global_Objects/Iterator", "Iterator")}} is deprecated.
Object methods
- {{jsxref("Global_Objects/Object/watch", "watch")}} and {{jsxref("Global_Objects/Object/unwatch", "unwatch")}} are deprecated. Use {{jsxref("Global_Objects/Proxy", "Proxy")}} instead.
__iterator__
is deprecated.
Date methods
- {{jsxref("Global_Objects/Date/getYear", "getYear")}} and {{jsxref("Global_Objects/Date/setYear", "setYear")}} are affected by the Year-2000-Problem and have been subsumed by {{jsxref("Global_Objects/Date/getFullYear", "getFullYear")}} and {{jsxref("Global_Objects/Date/setFullYear", "setFullYear")}}.
- You should use {{jsxref("Global_Objects/Date/toISOString", "toISOString")}} instead of the deprecated {{jsxref("Global_Objects/Date/toGMTString", "toGMTString")}} method in new code.
- {{jsxref("Global_Objects/Date/toLocaleFormat", "toLocaleFormat")}} is deprecated.
Funtion
- {{jsxref("Operators/Expression_closures", "Expression closures", "", 1)}} is deprecated. Use Regular {{jsxref("Operators/function", "function")}} or {{jsxref("Functions/Arrow_functions", "Arrow functions", "", 1)}} instead.
Proxy
- Proxy.create and Proxy.createFunction are deprecated. Use {{jsxref("Global_Objects/Proxy", "Proxy")}} API instead.
let
- {{jsxref("Statements/let", "let block", "#let_block")}} and {{jsxref("Statements/let", "let expressions", "#let_expressions")}} are deprecated.
Escape sequences
- Octal escape sequences (\ followed by one, two, or three octal digits) are deprecated in string and regular expression literals.
- The {{jsxref("Global_Objects/escape", "escape")}} and {{jsxref("Global_Objects/unescape", "unescape")}} functions are deprecated. Use {{jsxref("Global_Objects/encodeURI", "encodeURI")}}, jsxref("Global_Objects/encodeURIComponent", "encodeURIComponent")}}, {{jsxref("Global_Objects/decodeURI", "decodeURI")}} or {{jsxref("Global_Objects/decodeURIComponent", "decodeURIComponent")}} to encode and decode escape sequences for special characters.
String methods
- HTML wrapper methods like {{jsxref("String.prototype.fontsize")}} and {{jsxref("String.prototype.big")}}.
- {{jsxref("String.prototype.quote")}} is removed from Firefox 37.
- non standard
flags
parameter in {{jsxref("String.prototype.search")}}, {{jsxref("String.prototype.match")}}, and {{jsxref("String.prototype.replace")}} are deprecated.
Obsolete features
These obsolete features have been entirely removed from JavaScript and can no longer be used as of the indicated version of JavaScript.
Object
Property | Description |
---|---|
{{jsxref("Global_Objects/Object/count", "__count__")}} | Returns the number of enumerable properties directly on a user-defined object. |
{{jsxref("Global_Objects/Object/Parent", "__parent__")}} | Points to an object's context. |
Method | Description |
---|---|
{{jsxref("Global_Objects/Object/eval", "Object.prototype.eval()")}} | Evaluates a string of JavaScript code in the context of the specified object. |
Function
Property | Description |
---|---|
{{jsxref("Global_Objects/Function/arity", "arity")}} | Number of formal arguments. |
Number
- {{jsxref("Number.toInteger()")}}
ParallelArray
- {{jsxref("ParallelArray")}}
Statements
- {{jsxref("Statements/for_each...in", "for each...in")}} is deprecated. Use {{jsxref("Statements/for...of", "for...of")}} instead.
- Destructuring {{jsxref("Statements/for...in", "for...in")}} is deprecated. Use {{jsxref("Statements/for...of", "for...of")}} instead.
E4X
See E4X for more information.
Sharp variables
See Sharp variables in JavaScript for more information.