TypeError: null/undefined 没有属性

当您尝试访问 nullundefined 的属性时,就会出现 JavaScript 异常“null(或 undefined)没有属性”。它们没有任何属性。

消息

TypeError: Cannot read properties of undefined (reading 'x') (V8-based)
TypeError: Cannot destructure 'x' as it is undefined. (V8-based)
TypeError: Cannot destructure property 'x' of 'y' as it is undefined. (V8-based)
TypeError: null has no properties (Firefox)
TypeError: undefined has no properties (Firefox)
TypeError: undefined is not an object (evaluating 'undefined.x') (Safari)
TypeError: Right side of assignment cannot be destructured (Safari)

错误类型

哪里出错了?

nullundefined 都没有您可以访问的属性。因此,您不能对它们使用 属性访问器,也不能 解构 它们。

示例

null 和 undefined 没有属性

js
null.foo;
// TypeError: null has no properties

undefined.bar;
// TypeError: undefined has no properties

另请参阅