JavaScript错误:无法读取未定义的属性"includes" [英] JavaScript error: Cannot read property 'includes' of undefined

问题描述

我想检查 msgArr 数组中是否已经存在 data.objectId .为此，我正在运行以下代码:

I want to check if a data.objectId already exists in the array msgArr. For that I am running the code below:

var exists = msgArr.objectId.includes(data.objectId);

if(exists === false){
   msgArr.push({"objectId":data.objectId,"latLont":data.latLont,"isOnline":data.isOnline});
}

该数组如下所示:

var msgArr = [
  {isOnline:true,latLont:"123",objectId:"on0V04v0Y9"},
  {isOnline:true,latLont:"1",objectId:"FpWBmpo0RY"},
  {isOnline:true,latLont:"48343",objectId:"Qt6CRXQuqE"} 
 ]

我收到以下错误:

无法读取未定义的属性包含"

Cannot read property 'includes' of undefined

推荐答案

正如评论所说:javascript数组对象没有属性 objectId .
查看此数组中的对象，很显然它们具有对象，因此可以使用

As the comments say: the javascript array object has no property objectId.
Looking at the objects in this array it's clear that they have it, so to check if a certain element exists you can do so using Array.prototype.some method:

var exists = msgArr.some(o => o.objectId === data.objectId);

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