如何删除 TypeScript 警告：类型 '{}' 上不存在属性 'length'
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How to remove TypeScript warning: property 'length' does not exist on type '{}'
提问by RaelB
In a TypeScript file, I have defined a 3D array:
在 TypeScript 文件中，我定义了一个 3D 数组：
var myArr = ['one', [[19, 1], [13, 1], [86, 1], [12, 2]],
'two', [[83, 1], [72, 1], [16, 2]],
'three', [[4, 1]]];
function testArray(){
console.log(myArr[1].length);
}
I get a warning under the length property:
我在 length 属性下收到警告：
Property 'length' does not exist on type '{}'
类型“{}”上不存在属性“长度”
Is there something I can do to remove this warning?
我能做些什么来消除这个警告吗？
采纳答案by Ryan Cavanaugh
Option 1: upgrade to bleeding-edge compiler and get union types
选项 1：升级到前沿编译器并获得联合类型
Option 2: Add a type annotation to the variable declaration:
选项 2：在变量声明中添加类型注释：
var myArr: any[] = ['one', [[19, 1], [13, 1], [86, 1], [12, 2]],
'two', [[83, 1], [72, 1], [16, 2]],
'three', [[4, 1]]];
function testArray(){
console.log(myArr[1].length);
}
回答by RaelB
I read a similar post here: How can I stop "property does not exist on type JQuery" syntax errors when using Typescript?
我在这里阅读了类似的帖子： How can I stop "property does not exist on type JQuery" syntax errors when using Typescript?
Which explains that I can cast to <any>.
这解释了我可以转换为 <any>。
This worked for me:
这对我有用：
function testArray(){
console.log((<any>myArr[1]).length);
}
回答by RamTn
i faced this error before,you have to cast the type to any and when you use generics you have to extends.
我之前遇到过这个错误，你必须将类型转换为 any ，当你使用泛型时，你必须扩展。
check the example blow:
检查示例打击：
const result = <T extends any>(arr:T[]):T => {
return arr[arr.length - 1]
}
result([1,2,3])
