TS2345:“数字|数字"类型的参数未定义"不能分配给“数字"类型的参数 [英] TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'

问题描述

我正在尝试在打字稿中创建chrome扩展名.

I am trying to create a chrome extension in typescript.

我有以下代码，尝试从后台脚本向contentscript发送消息.

I have the following code, where I try to send a message to contentscript from the background script.

// background script 
chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
   chrome.tabs.sendMessage(tabs[0].id, {action: "open_dialog_box"}, function(response) {
      console.log(response);
   });  
});

但是打字稿出现以下错误

but typescript is giving the following error

ERROR in /Users/shobi/Projects/Chrome Extensions/src/js/background.ts(8,37)
      TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
  Type 'undefined' is not assignable to type 'number'.

我尝试使用parseInt()将id转换为整数，但是仍然不能防止错误发生.

I tried converting the id to an integer using parseInt(), but still its not preventing the error.

推荐答案

Chrome的标签.id可能未定义(因为它是

Chrome's tab .id is possibly undefined (because it's defined as optional in the type definitions), which means when using strictNullChecks you have to either use a non-null assertion:

tabs[0].id!

或编写代码以确保id不为空:

Or write code to ensure that id is not null:

if (tabs[0].id) { // send message

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