cannot read property 'length' of undefined
时间: 2023-04-30 10:02:47 浏览: 374
"length" 属性是 JavaScript 中的一个内置属性,它用于返回一个字符串或数组的长度。如果在程序中出现 "cannot read property length of undefined" 的错误消息,这通常表明该变量未定义或未初始化,因此不能读取其 "length" 属性。
相关问题
Cannot read property 'length' of undefined
"Cannot read property 'length' of undefined"错误通常是由于访问一个未定义或未赋值的变量或对象属性引起的。根据提供的引用内容,你遇到了一个名为"Cannot read property 'length' of undefined"的错误。这个错误发生在尝试读取一个未定义的属性的长度时。提供的错误信息和引用中关于小程序的说明,可以推断出这个错误可能与
TypeError: Cannot read property 'length' of undefined
This error occurs when you try to access the length property of a variable that is undefined.
For example:
```
let arr;
console.log(arr.length); // TypeError: Cannot read property 'length' of undefined
```
In this case, the variable `arr` is undefined and does not have a length property. To fix this error, you can initialize the variable with an empty array or check if the variable is defined before accessing its length property.
```
let arr = [];
console.log(arr.length); // 0
if (arr) {
console.log(arr.length); // 0
}
```