1.filter对数组对象去重时的特殊处理

1.filter通常情况下是用来返回一个符合条件的新数组的，并且他不会对原数组产生影响：

         comment_or_reply_id: "ob8qj0xq8e5s",
          from_uid: "1502039268@qq.com",
          isAgreeClick: true,
          topic_id: "604629fd0344202df0b22d81",
          topic_type: "nous_articles"
     },
     {
          comment_or_reply_id: "1",
          from_uid: "666",
          isAgreeClick: true,
          topic_id: "604629fd0344202df0b22d81",
          topic_type: "nous_articles"
     }
]
let crr = {
     from_uid: "1502039268@qq.com",
     comment_id: 'ob8qj0xq8e5s'
}
let b = arr.filter(function (curentV, index, arr) {
     return curentV.from_uid == crr.from_uid && curentV.comment_or_reply_id == crr.comment_id

})
console.log(b)

运行结果：

[
  {
    comment_or_reply_id: 'ob8qj0xq8e5s',
    from_uid: '1502039268@qq.com',
    isAgreeClick: true,
    topic_id: '604629fd0344202df0b22d81',
    topic_type: 'nous_articles'
  }
]

但是我只是要拿到里面的isAgreeClick怎么做呢？

这样吗：

let b = arr.filter(function (curentV, index, arr) {
     return curentV.from_uid == crr.from_uid && curentV.comment_or_reply_id == crr.comment_id

})[0].isAgreeClick
console.log(b)

运行结果：true，的确拿到了该值，但是此种做法的弊端就是，当filter里面的条件没有匹配到时，会返回一个空数组，此时对空数组取值就会报错！

例子：还是刚才那段代码，但是此时comment_or_reply_id为1了，此时匹配不到就会报错

let arr = [{
          comment_or_reply_id: "1",
          from_uid: "1502039268@qq.com",
          isAgreeClick: true,
          topic_id: "604629fd0344202df0b22d81",
          topic_type: "nous_articles"
     },
     {
          comment_or_reply_id: "1",
          from_uid: "666",
          isAgreeClick: true,
          topic_id: "604629fd0344202df0b22d81",
          topic_type: "nous_articles"
     }
]
let crr = {
     from_uid: "1502039268@qq.com",
     comment_id: 'ob8qj0xq8e5s'
}
let b = arr.filter(function (curentV, index, arr) {
     return curentV.from_uid == crr.from_uid && curentV.comment_or_reply_id == crr.comment_id

})[0].isAgreeClick
console.log(b)

 如何处理呢，下面给出方案：就是把后面数组的返回结果附上布尔值，就可以进行拿到里面的bool值了，但是此种做法只针对布尔值有效，想要拿到里面的其它类型元素的值，

而且在空数组我下仍然不会报错的话，我暂时没有思路。

let b = arr.filter(function (curentV, index, arr) {
     return curentV.from_uid == crr.from_uid && curentV.comment_or_reply_id == crr.comment_id

})==false
console.log(b)

上面运行结果：