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JavaScript . . , . , .

In this article

.

return

, .

break

, , .

continue

.

throw

.

if...else

, . , .

switch

, , .

try...catch

.

var

, .

let

, .

const

.

function

.

function*

-, .

async function

.

async function*

-, .

class

.

do...while

, , false. , .

for

, , , .

for...in

. .

for...of

( , , ), .

for await...of

, , , .

while

, , true. ..

, , JavaScript .

. .

. , .

debugger

. , .

export

, . Netscape ECMAScript 6.

import

, , . Netscape ECMAScript 6.

label

, break continue.

with

.

Specification
ECMAScript 2027 LanguageSpecification
# prod-FormalParameters
ECMAScript 2027 LanguageSpecification
# sec-generator-function-definitions
ECMAScript 2027 LanguageSpecification
# sec-return-statement
ECMAScript 2027 LanguageSpecification
# sec-imports
ECMAScript 2027 LanguageSpecification
# sec-break-statement
ECMAScript 2027 LanguageSpecification
# sec-while-statement
ECMAScript 2027 LanguageSpecification
# sec-empty-statement
ECMAScript 2027 LanguageSpecification
# sec-throw-statement
ECMAScript 2027 LanguageSpecification
# sec-debugger-statement
ECMAScript 2027 LanguageSpecification
# prod-ModuleExportName
ECMAScript 2027 LanguageSpecification
# sec-generatorresume
ECMAScript 2027 LanguageSpecification
# sec-for-in-and-for-of-statements
ECMAScript 2027 LanguageSpecification
# sec-for-statement
ECMAScript 2027 LanguageSpecification
# sec-async-generator-function-definitions
ECMAScript 2027 LanguageSpecification
# sec-block
ECMAScript 2027 LanguageSpecification
# sec-let-and-const-declarations
ECMAScript 2027 LanguageSpecification
# sec-exports
ECMAScript 2027 LanguageSpecification
# sec-try-statement
ECMAScript 2027 LanguageSpecification
# sec-iteratorclose
ECMAScript 2027 LanguageSpecification
# sec-class-definitions
ECMAScript 2027 LanguageSpecification
# prod-WithClause
ECMAScript 2027 LanguageSpecification
# sec-labelled-statements
ECMAScript 2027 LanguageSpecification
# sec-if-statement
ECMAScript 2027 LanguageSpecification
# sec-async-function-definitions
ECMAScript 2027 LanguageSpecification
# sec-function-definitions
ECMAScript 2027 LanguageSpecification
# sec-with-statement
ECMAScript 2027 LanguageSpecification
# sec-continue-statement
ECMAScript 2027 LanguageSpecification
# sec-variable-statement
ECMAScript 2027 LanguageSpecification
# sec-switch-statement
ECMAScript 2027 LanguageSpecification
# sec-do-while-statement
ECMAScript Async Explicit Resource Management
# sec-let-and-const-declarations
Service Workers Nightly
# dom-registrationoptions-type
HTML
# css-module-script
HTML
# fetch-a-single-module-script
HTML
# json-module-script
HTML
# dom-worklet-addmodule
HTML
# text-module-script
HTML
# fetch-a-module-worker-script-tree
Source Phase Imports
# sec-imports
WebAssembly JavaScript Interface: ESM Integration
# esm-integration
Deferred Imports Evaluation
# sec-imports

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  1. JavaScript
  3. JavaScript
    7. Numbers and strings
    8. Representing dates & times
    13. Using classes
    15. JavaScript
    17. Resource management
    18. Internationalization
    19. JavaScript
    1. Language overview
    2. JavaScript
    1. AbstractModuleSource
    2. AggregateError
    3. Array
    4. ArrayBuffer
    5. AsyncDisposableStack
    6. AsyncFunction
    7. AsyncGenerator
    8. AsyncGeneratorFunction
    9. AsyncIterator
    10. Atomics
    11. BigInt
    12. BigInt64Array
    13. BigUint64Array
    14. Boolean
    15. DataView
    17. decodeURI()
    18. decodeURIComponent()
    19. DisposableStack
    20. encodeURI()
    21. encodeURIComponent()
    22. Error
    23. escape()
    24. eval()
    25. EvalError
    26. FinalizationRegistry
    27. Float16Array
    28. Float32Array
    29. Float64Array
    30. Function
    31. Generator
    32. GeneratorFunction
    33. globalThis
    34. Infinity
    35. Int8Array
    36. Int16Array
    37. Int32Array
    38. InternalError
    39. Intl
    40. isFinite()
    41. isNaN
    42. Iterator
    43. JSON
    44. Map
    45. Math
    46. NaN
    47. Number
    48. Object
    49. parseFloat()
    50. parseInt()
    51. Promise
    53. RangeError
    54. ReferenceError
    55. Reflect
    56. RegExp
    57. Set
    58. SharedArrayBuffer
    59. String
    60. SuppressedError
    61. Symbol
    62. SyntaxError
    63. Temporal
    64. TypedArray
    65. TypeError
    66. Uint8Array
    67. Uint8ClampedArray
    68. Uint16Array
    69. Uint32Array
    70. undefined
    71. unescape()
    72. URIError
    73. WeakMap
    74. WeakRef
    75. WeakSet
    1. (+)
    2. (+=)
    3. (=)
    4. async function expression
    5. async function* expression
    6. await
    7. Bitwise AND (&)
    8. Bitwise AND assignment (&=)
    9. Bitwise NOT (~)
    10. Bitwise OR (|)
    11. Bitwise OR assignment (|=)
    12. Bitwise XOR (^)
    13. Bitwise XOR assignment (^=)
    14. class expression
    16. ()
    17. (--)
    18. delete
    20. Division (/)
    21. Division assignment (/=)
    22. (==)
    23. Exponentiation (**)
    24. Exponentiation assignment (**=)
    26. function* expression
    27. Greater than (>)
    28. Greater than or equal (>=)
    30. import.meta
      1. import.meta.resolve()
    31. import()
      1. import.defer()
      2. import.source()
    32. in
    33. Increment (++)
    34. (!=)
    35. instanceof
    36. Left shift (<<)
    37. Left shift assignment (<<=)
    38. Less than (<)
    39. Less than or equal (<=)
    40. (&&)
    41. (&&=)
    42. (!)
    43. (||)
    44. (||=)
    45. Multiplication (*)
    46. Multiplication assignment (*=)
    47. new
    48. new.target
    49. null
    50. (??=)
    51. (??)
    55. Property accessors
    56. Remainder (%)
    57. Remainder assignment (%=)
    58. Right shift (>>)
    59. Right shift assignment (>>=)
    60. Spread syntax
    61. (===)
    62. (!==)
    63. Subtraction (-)
    64. Subtraction assignment (-=)
    65. super
    66. this
    67. typeof
    68. Unary negation (-)
    69. Unary plus (+)
    70. Unsigned right shift (>>>)
    71. Unsigned right shift assignment (>>>=)
    72. void operator
    73. yield
    74. yield*
    1. async function
    2. async function*
    3. await using
    5. break
    6. class
    7. const
    8. continue
    9. debugger
    10. do...while
    12. export
    13. Expression statement
    14. for
    15. for await...of
    16. for...in
    17. for...of
    18. function
    19. function*
    20. if...else
    21. import
      1. Import attributes
      2. import defer
      3. import source
    23. let
    24. return
    25. switch
    26. throw
    27. try...catch
    28. using
    29. var
    30. while
    31. with
    3. getter
    5. (rest parameters)
    6. setter
    7. arguments
      1. [Symbol.iterator]()
      2. arguments.callee
      3. arguments.length
    1. constructor
    2. extends
    5. static
    6. Static initialization blocks
    1. Backreference: \1, \2
    2. Buffer boundary assertion: \A, \z, \Z
    3. Capturing group: (...)
    4. Character class escape: \d, \D, \w, \W, \s, \S
    5. Character class: [...], [^...]
    6. Character escape: \n, \u{...}
    7. Disjunction: |
    8. Input boundary assertion: ^, $
    9. Literal character: a, b
    10. Lookahead assertion: (?=...), (?!...)
    11. Lookbehind assertion: (?<=...), (?<!...)
    12. Modifier: (?ims-ims:...)
    13. Named backreference: \k<name>
    14. Named capturing group: (?<name>...)
    15. Non-capturing group: (?:...)
    16. Quantifier: *, +, ?, {n}, {n,}, {n,m}
    17. Unicode character class escape: \p{...}, \P{...}
    18. Wildcard: .
    19. Word boundary assertion: \b, \B
    1. AggregateError: No Promise in Promise.any was resolved
    2. Error: Permission denied to access property "x"
    3. InternalError: too much recursion
    4. RangeError: argument is not a valid code point
    5. RangeError: BigInt division by zero
    6. RangeError: BigInt negative exponent
    7. RangeError: form must be one of 'NFC', 'NFD', 'NFKC', or 'NFKD'
    8. RangeError: invalid array length
    9. RangeError: invalid date
    10. RangeError: precision is out of range
    11. RangeError: radix must be an integer
    12. RangeError: repeat count must be less than infinity
    13. RangeError: repeat count must be non-negative
    14. RangeError: x can't be converted to BigInt because it isn't an integer
    15. ReferenceError: "x" is not defined
    16. ReferenceError: assignment to undeclared variable "x"
    17. ReferenceError: can't access lexical declaration 'X' before initialization
    18. ReferenceError: must call super constructor before using 'this' in derived class constructor
    19. ReferenceError: super() called twice in derived class constructor
    20. SyntaxError: 'arguments'/'eval' can't be defined or assigned to in strict mode code
    21. SyntaxError: "0"-prefixed octal literals and octal escape seq. are deprecated
    22. SyntaxError: "use strict" not allowed in function with non-simple parameters
    23. SyntaxError: "x" is a reserved identifier
    24. SyntaxError: \ at end of pattern
    25. SyntaxError: a declaration in the head of a for-of loop can't have an initializer
    26. SyntaxError: applying the 'delete' operator to an unqualified name is deprecated
    27. SyntaxError: arguments is not valid in fields
    28. SyntaxError: await is only valid in async functions, async generators and modules
    29. SyntaxError: await/yield expression can't be used in parameter
    30. SyntaxError: cannot use ?? unparenthesized within || and && expressions
    31. SyntaxError: character class escape cannot be used in class range in regular expression
    32. SyntaxError: continue must be inside loop
    33. SyntaxError: duplicate capture group name in regular expression
    34. SyntaxError: duplicate formal argument x
    35. SyntaxError: for-in loop head declarations may not have initializers
    36. SyntaxError: function statement requires a name( )
    37. SyntaxError: functions cannot be labelled
    38. SyntaxError: getter and setter for private name #x should either be both static or non-static
    39. SyntaxError: getter functions must have no arguments
    40. SyntaxError: identifier starts immediately after numeric literal
    41. SyntaxError: illegal character
    42. SyntaxError: import declarations may only appear at top level of a module
    43. SyntaxError: incomplete quantifier in regular expression
    44. ReferenceError: invalid assignment left-hand side
    45. SyntaxError: invalid BigInt syntax
    46. SyntaxError: invalid capture group name in regular expression
    47. SyntaxError: invalid character in class in regular expression
    48. SyntaxError: invalid class set operation in regular expression
    49. SyntaxError: invalid decimal escape in regular expression
    50. SyntaxError: invalid identity escape in regular expression
    51. SyntaxError: invalid named capture reference in regular expression
    52. SyntaxError: invalid property name in regular expression
    53. SyntaxError: invalid range in character class
    54. SyntaxError: invalid regexp group
    55. SyntaxError: invalid regular expression flag "x"
    56. SyntaxError: invalid unicode escape in regular expression
    57. SyntaxError: JSON.parse: bad parsing
    58. SyntaxError: label not found
    59. SyntaxError: missing : after property id
    60. : ")"
    61. SyntaxError: missing ) after condition
    62. SyntaxError: missing ] after element list
    63. SyntaxError: missing } after function body
    64. SyntaxError: missing } after property list
    65. SyntaxError: missing = in const declaration
    66. SyntaxError: missing formal parameter( )
    67. SyntaxError: missing name after . operator( . )
    68. SyntaxError: missing variable name
    69. SyntaxError: negated character class with strings in regular expression
    70. SyntaxError: new keyword cannot be used with an optional chain
    71. SyntaxError: nothing to repeat
    72. SyntaxError: numbers out of order in {} quantifier.
    73. SyntaxError: octal escape sequences can't be used in untagged template literals or in strict mode code
    74. SyntaxError: parameter after rest parameter
    75. SyntaxError: private fields can't be deleted
    76. SyntaxError: property name __proto__ appears more than once in object literal
    77. SyntaxError: raw bracket is not allowed in regular expression with unicode flag
    78. SyntaxError: redeclaration of formal parameter "x"
    79. SyntaxError: reference to undeclared private field or method #x
    80. SyntaxError: rest parameter may not have a default
    81. SyntaxError: return not in function
    82. SyntaxError: setter functions must have one argument
    83. SyntaxError: string literal contains an unescaped line break
    84. SyntaxError: super() is only valid in derived class constructors
    85. SyntaxError: tagged template cannot be used with optional chain
    86. SyntaxError: Unexpected '#' used outside of class body
    87. SyntaxError: Unexpected token
    88. SyntaxError: unlabeled break must be inside loop or switch
    89. SyntaxError: unparenthesized unary expression can't appear on the left-hand side of '**'
    90. SyntaxError: use of super property/member accesses only valid within methods or eval code within methods
    91. SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead
    92. :
    93. TypeError: 'x' is not iterable ( 'x' )
    94. TypeError: "x" is (not) "y"
    95. TypeError: "x" is not a constructor
    96. TypeError: "x" is not a function
    97. TypeError: "x" is not a non-null object( : "x" )
    98. TypeError: "x" is read-only( : "x" )
    99. TypeError: already executing generator
    100. TypeError: BigInt value can't be serialized in JSON
    101. TypeError: calling a builtin X constructor without new is forbidden
    102. TypeError: can't access/set private field or method: object is not the right class
    103. TypeError: can't assign to property "x" on "y": not an object
    104. TypeError: can't convert BigInt to number
    105. TypeError: can't convert x to BigInt
    106. TypeError: can't define property "x": "obj" is not extensible
    107. TypeError: can't delete non-configurable array element( : )
    108. TypeError: can't redefine non-configurable property "x"
    109. TypeError: can't set prototype of this object
    110. TypeError: can't set prototype: it would cause a prototype chain cycle
    111. TypeError: cannot use 'in' operator to search for 'x' in 'y'( 'in' 'x' 'y')
    112. TypeError: class constructors must be invoked with 'new'
    113. TypeError: cyclic object value
    114. TypeError: derived class constructor returned invalid value x
    115. TypeError: getting private setter-only property
    116. TypeError: Initializing an object twice is an error with private fields/methods
    117. TypeError: invalid 'instanceof' operand 'x'( : '' '')
    118. TypeError: invalid Array.prototype.sort argument (TypeError: Array.prototype.sort argument)
    119. TypeError: invalid assignment to const "x"( const "x")
    120. TypeError: Iterator/AsyncIterator constructor can't be used directly
    121. TypeError: matchAll/replaceAll must be called with a global RegExp
    122. TypeError: More arguments needed
    123. TypeError: "x" has no properties
    124. TypeError: property "x" is non-configurable and can't be deleted( "x" )
    125. TypeError: Reduce of empty array with no initial value( : )
    126. TypeError: setting getter-only property "x"( "x")
    127. TypeError: WeakSet key/WeakMap value 'x' must be an object or an unregistered symbol
    128. X.prototype.y called on incompatible type
    129. URIError: malformed URI sequence
    130. Warning: -file- is being assigned a //# sourceMappingURL, but already has one
    131. Warning: unreachable code after return statement
    1. JavaScript
    2. Execution model
    4. Magic comments
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