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TypeError: property "x" is non-configurable and can't be deleted

消息

TypeError: property "x" is non-configurable and can't be deleted. (Firefox) TypeError: Cannot delete property 'x' of #<Object> (Chrome)

本文内容

错误类型

TypeError 只出现在严格模式下。

哪里有问题？

尝试删除某个属性，但是这个属性是不可配置的。configurable 属性控制是否该属性能从对象上删除，以及它的属性（除了writable）能否被修改。

这个错误仅仅在严格模式下出现。在非严格模式下，这个操作返回 false。

示例

不可配置的属性并不特别常见，但是它们可以使用 Object.defineProperty() 或 Object.freeze() 创建。

js
"use strict"; var obj = Object.freeze({ name: "Elsa", score: 157 }); delete obj.score; // TypeError ("use strict"); var obj = {}; Object.defineProperty(obj, "foo", { value: 2, configurable: false }); delete obj.foo; // TypeError ("use strict"); var frozenArray = Object.freeze([0, 1, 2]); frozenArray.pop(); // TypeError

也有一些内建于 JavaScript 的不可配置属性。你可能会尝试删除一个数学常量。

js
"use strict"; delete Math.PI; // TypeError

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  1. JavaScript
  2. 教程
  3. JavaScript 指南
    1. 介绍
    2. 语法和数据类型
    3. 流程控制与错误处理
    4. 循环与迭代
    5. 函数
    6. 表达式与运算符
    7. 数字与字符串
    8. 表达日期与时间
    9. 正则表达式
    10. 索引集合类
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    12. 使用对象
    13. 使用类
    14. 使用 Promise
    15. JavaScript 类型化数组
    16. 迭代器和生成器
    17. 资源管理
    18. 国际化
    19. JavaScript 模块
  4. 中级
    1. 语言概述
    2. JavaScript 数据结构
    3. 如何正确判断相等性
    4. 属性的可枚举性和所有权
    5. 闭包
  5. 高级
    1. 继承和原型链
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  6. 参考
  7. 内置对象
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    2. Array
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    8. AsyncIterator
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  8. 表达式和运算符
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    16. Unicode 字符类转义：\p{...}、\P{...}
    17. 通配符：.
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  13. 错误
    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
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    20. SyntaxError: 'arguments'/'eval' can't be defined or assigned to in strict mode code
    21. SyntaxError: "0"-prefixed octal literals are deprecated
    22. SyntaxError: "use strict" not allowed in function with non-simple parameters
    23. SyntaxError: "x" is a reserved identifier
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    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
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    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
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    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. SyntaxError: 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. SyntaxError: missing ) after argument list
    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. ReferenceError: deprecated caller or arguments usage
    93. TypeError: 'x' is not iterable
    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
    98. TypeError: "x" is read-only
    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: invalid 'in' operand "x"
    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
    119. TypeError: invalid assignment to 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
    125. TypeError: Reduce of empty array with no initial value
    126. TypeError: setting getter-only property "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
  14. 更多
    1. JavaScript 技术概要
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    3. 词法文法
    4. 迭代协议
    5. 严格模式
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