非常教程

JavaScript参考手册

错误 | Errors

Errors: Undefined prop

信息

ReferenceError: reference to undefined property "x" (Firefox)

错误类型

ReferenceError 仅在严格模式下警告。

哪里出错了?

该脚本试图访问不存在的对象属性。有两种访问属性的方法; 请参阅属性访问器参考页面以了解更多关于它们的信息。

有关未定义属性引用的错误仅出现在严格模式代码中。在非严格的代码中,对不存在的属性的访问被忽略。

示例

无效的情况

在这种情况下,该属性bar是一个未定义的属性,所以ReferenceError会发生。

'use strict'; 

var foo = {};
foo.bar; // ReferenceError: reference to undefined property "bar"

有效的情况

为了避免错误,您需要为bar对象添加一个定义,或者bar在尝试访问该对象之前检查该属性是否存在; 一种方法是使用该Object.prototype.hasOwnProperty()方法),如下所示:

'use strict';

var foo = {};

// Define the bar property

foo.bar = 'moon';
console.log(foo.bar); // "moon"

// Test to be sure bar exists before accessing it

if (foo.hasOwnProperty('bar') {
  console.log(foo.bar);
}

错误 | Errors相关

1.Error
2.error.message
3.error.name
4.Error.prototype
5.error.toString
6.Errors
7.Errors: Already has pragma
8.Errors: Array sort argument
9.Errors: Bad octal
10.Errors: Bad radix
11.Errors: Bad regexp flag
12.Errors: Bad return or yield
13.Errors: Called on incompatible type
14.Errors: Cant access lexical declaration before init
15.Errors: Cant define property object not extensible
16.Errors: Cant delete
17.Errors: Cant redefine property
18.Errors: Cyclic object value
19.Errors: Dead object
20.Errors: Delete in strict mode
21.Errors: Deprecated caller or arguments usage
22.Errors: Deprecated expression closures
23.Errors: Deprecated octal
24.Errors: Deprecated source map pragma
25.Errors: Deprecated String generics
26.Errors: Deprecated toLocaleFormat
27.Errors: Equal as assign
28.Errors: For-each-in loops are deprecated
29.Errors: Getter only
30.Errors: Identifier after number
31.Errors: Illegal character
32.Errors: in operator no object
33.Errors: Invalid array length
34.Errors: Invalid assignment left-hand side
35.Errors: Invalid const assignment
36.Errors: Invalid date
37.Errors: Invalid for-in initializer
38.Errors: Invalid for-of initializer
39.Errors: JSON bad parse
40.Errors: Malformed formal parameter
41.Errors: Malformed URI
42.Errors: Missing bracket after list
43.Errors: Missing colon after property id
44.Errors: Missing curly after function body
45.Errors: Missing curly after property list
46.Errors: Missing formal parameter
47.Errors: Missing initializer in const
48.Errors: Missing name after dot operator
49.Errors: Missing parenthesis after argument list
50.Errors: Missing parenthesis after condition
51.Errors: Missing semicolon before statement
52.Errors: More arguments needed
53.Errors: Negative repetition count
54.Errors: No non-null object
55.Errors: No properties
56.Errors: No variable name
57.Errors: Non configurable array element
58.Errors: Not a codepoint
59.Errors: Not a constructor
60.Errors: Not a function
61.Errors: Not defined
62.Errors: Precision range
63.Errors: Property access denied
64.Errors: Read-only
65.Errors: Redeclared parameter
66.Errors: Reserved identifier
67.Errors: Resulting string too large
68.Errors: Stmt after return
69.Errors: Strict Non Simple Params
70.Errors: Too much recursion
71.Errors: Typed array invalid arguments
72.Errors: Undeclared var
73.Errors: Unexpected token
74.Errors: Unexpected type
75.Errors: Unnamed function statement
76.Errors: Unterminated string literal
77.Errors: Var hides argument
78.EvalError
79.EvalError.prototype
80.RangeError
81.RangeError.prototype
82.ReferenceError
83.ReferenceError.prototype
84.SyntaxError
85.SyntaxError.prototype
86.TypeError
87.TypeError.prototype
88.URIError
89.URIError.prototype
JavaScript

JavaScript 是一种高级编程语言,通过解释执行,是一门动态类型,面向对象(基于原型)的解释型语言。它已经由ECMA(欧洲电脑制造商协会)通过 ECMAScript 实现语言的标准化。它被世界上的绝大多数网站所使用,也被世界主流浏览器( Chrome、IE、FireFox、Safari、Opera )支持。JavaScript 是一门基于原型、函数先行的语言,是一门多范式的语言,它支持面向对象编程,命令式编程,以及函数式编程。它提供语法来操控文本、数组、日期以及正则表达式等,不支持 I/O,比如网络