TypeError: "x" has no properties

错误信息

TypeError: null has no properties
TypeError: undefined has no properties

错误类型

TypeError.

哪里出错了?

 null 和 undefined中，没有你需要的属性。

例子

null.foo;
// 错误类型: null没有这个属性

undefined.bar;
// 错误类型: undefined没有这个属性

参考

相关主题
  1. JavaScript
  2. 教程:
  3. 快速入门
    1. JavaScript 基础知识
    2. JavaScript first steps
    3. JavaScript building blocks
    4. Introducing JavaScript objects
  4. JavaScript 指南
    1. Introduction
    2. Grammar and types
    3. Control flow and error handling
    4. Loops and iteration
    5. Functions
    6. Expressions and operators
    7. Numbers and dates
    8. Text formatting
    9. Regular expressions
    10. Indexed collections
    11. Keyed collections
    12. Working with objects
    13. Details of the object model
    14. Using promises
    15. Iterators and generators
    16. Meta programming
  5. 中级教程
    1. Introducing JavaScript objects
    2. Client-side web APIs
    3. 深入 JavaScript
    4. JavaScript 数据结构
    5. 如何正确判断相等性
    6. Closures
  6. 高级
    1. 继承和原型链
    2. 严格模式
    3. JavaScript 类型化数组
    4. 内存管理
    5. Concurrency model and Event Loop
  7. 引用:
  8. 内置对象
    1. Array
    2. ArrayBuffer
    3. AsyncFunction
    4. Atomics
    5. BigInt
    6. Boolean
    7. DataView
    8. Date
    9. Error
    10. EvalError
    11. Float32Array
    12. Float64Array
    13. Function
    14. Generator
    15. GeneratorFunction
    16. Infinity
    17. Int16Array
    18. Int32Array
    19. Int8Array
    20. InternalError
    21. Intl
    22. Intl.Collator
    23. Intl.DateTimeFormat
    24. Intl.ListFormat [我来译!]
    25. Intl.NumberFormat
    26. Intl.PluralRules
    27. Intl.RelativeTimeFormat [我来译!]
    28. JSON
    29. Map
    30. Math
    31. NaN
    32. Number
    33. Object
    34. Promise
    35. Proxy
    36. RangeError
    37. ReferenceError
    38. Reflect
    39. RegExp
    40. Set
    41. SharedArrayBuffer
    42. String
    43. Symbol
    44. SyntaxError
    45. TypeError
    46. TypedArray
    47. URIError
    48. Uint16Array
    49. Uint32Array
    50. Uint8Array
    51. Uint8ClampedArray
    52. WeakMap
    53. WeakSet
    54. WebAssembly
    55. decodeURI()
    56. decodeURIComponent()
    57. encodeURI()
    58. encodeURIComponent()
    59. escape()
    60. eval()
    61. isFinite()
    62. isNaN()
    63. null
    64. parseFloat
    65. parseInt
    66. undefined
    67. unescape()
    68. uneval()
  9. 表达式和运算符
    1. 算术运算符
    2. 数组推导式
    3. 赋值运算符
    4. 按位操作符
    5. 逗号操作符
    6. 比较操作符
    7. 条件运算符
    8. 解构赋值
    9. Expression closures
    10. Generator推导式
    11. 圆括号运算符
    12. 旧式生成器函数
    13. 逻辑运算符
    14. 对象初始化
    15. 运算符优先级
    16. 管道操作符
    17. 属性访问器
    18. 展开语法
    19. async function expression
    20. await
    21. 类表达式
    22. delete 操作符
    23. 函数表达式
    24. function* 表达式
    25. in
    26. instanceof
    27. new运算符
    28. new.target
    29. super
    30. this
    31. typeof
    32. void 运算符
    33. yield
    34. yield*
  10. 语句和声明
    1. 遗留的生成器函数
    2. async function
    3. block
    4. break
    5. class
    6. const
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    23. label
    24. let
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    27. throw
    28. try...catch
    29. var
    30. while
    31. with
  11. 函数
    1. 箭头函数
    2. 默认参数值
    3. 方法的定义
    4. 剩余参数
    5. Arguments 对象
    6. getter
    7. setter
  12. Classes
    1. 构造方法
    2. extends
    3. static
  13. Errors
    1. Error: Permission denied to access property "x"
    2. InternalError: too much recursion
    3. RangeError: argument is not a valid code point
    4. RangeError: invalid array length
    5. RangeError: invalid date
    6. RangeError: precision is out of range
    7. RangeError: radix must be an integer
    8. RangeError: repeat count must be less than infinity
    9. RangeError: repeat count must be non-negative
    10. ReferenceError: "x" is not defined
    11. ReferenceError: assignment to undeclared variable "x"
    12. ReferenceError: can't access lexical declaration`X' before initialization
    13. ReferenceError: deprecated caller or arguments usage
    14. ReferenceError: invalid assignment left-hand side
    15. ReferenceError: reference to undefined property "x"
    16. SyntaxError: "0"-prefixed octal literals and octal escape seq. are deprecated
    17. SyntaxError: "use strict" not allowed in function with non-simple parameters
    18. SyntaxError: "x" is a reserved identifier
    19. SyntaxError: JSON.parse: bad parsing
    20. SyntaxError: Malformed formal parameter
    21. SyntaxError: Unexpected token
    22. SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead
    23. SyntaxError: a declaration in the head of a for-of loop can't have an initializer
    24. SyntaxError: applying the 'delete' operator to an unqualified name is deprecated
    25. SyntaxError: for-in loop head declarations may not have initializers
    26. SyntaxError: function statement requires a name
    27. SyntaxError: identifier starts immediately after numeric literal
    28. SyntaxError: illegal character
    29. SyntaxError: invalid regular expression flag "x"
    30. SyntaxError: missing ) after argument list
    31. SyntaxError: missing ) after condition
    32. SyntaxError: missing : after property id
    33. SyntaxError: missing ; before statement
    34. SyntaxError: missing = in const declaration
    35. SyntaxError: missing ] after element list
    36. SyntaxError: missing formal parameter
    37. SyntaxError: missing name after . operator
    38. SyntaxError: missing variable name
    39. SyntaxError: missing } after function body
    40. SyntaxError: missing } after property list
    41. SyntaxError: redeclaration of formal parameter "x"
    42. SyntaxError: return not in function
    43. SyntaxError: test for equality (==) mistyped as assignment (=)?
    44. SyntaxError: unterminated string literal
    45. TypeError: "x" has no properties
    46. TypeError: "x" is (not) "y"
    47. TypeError: "x" is not a constructor
    48. TypeError: "x" is not a function
    49. TypeError: "x" is not a non-null object
    50. TypeError: "x" is read-only
    51. TypeError: 'x' is not iterable
    52. TypeError: More arguments needed
    53. 类型错误：在没有初始值的情况下简化空数组
    54. TypeError: can't access dead object
    55. TypeError: can't access property "x" of "y"
    56. TypeError: can't define property "x": "obj" is not extensible
    57. TypeError: can't delete non-configurable array element
    58. TypeError: can't redefine non-configurable property "x"
    59. TypeError: invalid 'in' operand "x"
    60. TypeError: cyclic object value
    61. TypeError: invalid 'instanceof' operand 'x'
    62. TypeError: invalid Array.prototype.sort argument
    63. TypeError: invalid arguments
    64. TypeError: invalid assignment to const "x"
    65. TypeError: property "x" is non-configurable and can't be deleted
    66. TypeError: setting getter-only property "x"
    67. TypeError: variable "x" redeclares argument
    68. URIError: malformed URI sequence
    69. Warning: -file- is being assigned a //# sourceMappingURL, but already has one
    70. SyntaxError: "x" is not a legal ECMA-262 octal constant
    71. Warning: Date.prototype.toLocaleFormat is deprecated
    72. Warning: JavaScript 1.6's for-each-in loops are deprecated
    73. Warning: String.x is deprecated; use String.prototype.x instead
    74. Warning: expression closures are deprecated
    75. Warning: unreachable code after return statement
    76. X.prototype.y called on incompatible type
  14. 更多
    1. JavaScript 知识概要
    2. 词法文法
    3. JavaScript 数据结构
    4. 属性的可枚举性和所有权
    5. Iteration protocols
    6. 严格模式
    7. 切换到严格模式
    8. 模板字符串
    9. 已废弃的特性
  15. New in JavaScript
    1. Mozilla 对 ECMAScript 6 的支持
    2. ECMAScript 5 support in Mozilla
    3. Mozilla对下一代ECMAScript 的支持
    4. Firefox 中的 JavaScript 更新日志
    5. JavaScript 1.1的新特性
    6. JavaScript 1.2的新特性
    7. JavaScript 1.3的新特性
    8. JavaScript 1.4的新特性
    9. JavaScript 1.5 的新特性
    10. JavaScript 1.6 的新特性
    11. JavaScript 1.7 的新特性
    12. New in JavaScript 1.8
    13. JavaScript 1.8.1 的新特性
    14. JavaScript 1.8.5 的新特性
  16. 文档:
  17. 常用列表
    1. 全部页面索引
    2. 方法索引
    3. 属性索引
    4. 拥有 "JavaScript" 标签的页面
  18. 贡献
    1. JavaScript 文档翻译状态
    2. MDN 项目