forEachjavascript中未定义的变量

如何解决forEachjavascript中未定义的变量

使用此简单函数遍历数组并显示元素，索引和类型，im尝试为以元音开头的单词在单词a上添加“ n”。例如。一个数字，一个对象。

但是添加n的变量“ n”在最终控制台中未定义。

我相信它的作用域错误，但是是javascript im寻求帮助的新手

const someArr = [
  'max',34,true,{
    name: 'sandra',student: true
  },['javascript','mongodb','react']
];

////////////////

function arrayTypeFinder(array) {
  someArr.forEach((elem,index) => {

    let type = typeof elem;

    if (type.charAt(0) === "a" || "e" || "i" || "o" || "u") {
      let n = "n"
    } else {
      let n = ""
    }

    console.log(`element ${elem} at index number: ${index} is a${n} ${type}`)
  })
}

///////////

arrayTypeFinder(someArr) //=> n is not defined

解决方法

您需要在条件之外定义外部

let n = ""
if (type.charAt(0) === "a" || "e" || "i" || "o" || "u") {
    n = "n"
}

或者您可以这样使用

let n= (type.charAt(0) === "a" || "e" || "i" || "o" || "u") ? "n" :"";

,

一种选择是使用[Unit] Before=network-pre.target Wants=network-pre.target [Service] # braise enable ensures hooks are setup into the network manager. ExecStart=/usr/bin/braise enable # The firewall is called by the nework manager. RemainAfterExit=yes ExecReload=/usr/bin/braise reload [Install] WantedBy=multi-user.target 而不是var。

这样，在所有相关范围内声明了let 。分配前具有n的值：

undefined

,

结合使用您的答案就可以了！谢谢！

function arrayTypeFinder(array) {
  someArr.forEach((elem,index) => {

    let type = typeof elem;

    let n = (type.charAt(0) === "a" || type.charAt(0) === "e" || type.charAt(0) === "i" || type.charAt(0) === "o" || type.charAt(0) === "u") ? "n" : "";

    console.log(`element ${elem} at index number: ${index} is a${n} ${type}`)
  })
}