循环的结果无法正常工作

Question

1. 我想循环遍历一个数组。
2. 任何长度大于 3 的索引我都想缩写。
3. 我想将新的缩写月份放入一个新数组中。
4. 我想通过将结果写入控制台来测试它是否有效。

我可以让代码运行，但是结果并不如我所愿。据我了解，循环运行为真，运行 if 语句，运行为真，运行代码块。之后，循环应该迭代并继续，只要 i

var months = ["January", "Febuary", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var monthsAbbrev = [];

for (var i = 0; i < months.length; i++) {
if (months[i].length > 3) {
monthsAbbrev = months[i].slice(0, 3);
}
}

console.log(monthsAbbrev);

Answer 1

你可以通过Array.prototype.map()简单地做到这一点

var months = ["January", "Febuary"]; //sample data for better understanding
var monthsAbbrev = months.map(v => v.substr(0,3));
console.log(monthsAbbrev); //["Jan", "Feb"]

顺便说一句，您在代码中的目标数组中没有任何pushing，这就是问题所在。

Answer 2

除了推送之外，您可以省略长度 > 3 的检查，因为 slice 已经在这样做了，这样可以防止错过某个月份，例如 'May'。

var months = ["January", "Febuary", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var monthsAbbrev = [];

for (var i = 0; i < months.length; i++) {
    monthsAbbrev.push(months[i].slice(0, 3));
}

console.log(monthsAbbrev);

Answer 3

您需要将月份添加到您的monthsAbbrev 数组中。一种方法是使用.push() 函数：

var months = ["January", "Febuary", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var monthsAbbrev = [];

for (var i = 0; i < months.length; i++) {
  if (months[i].length > 3) {
    monthsAbbrev.push(months[i].slice(0, 3));
  }
}

console.log(monthsAbbrev);

Answer 4

你只需要推动形成的数组。休息一下吧。

var months = ["January", "Febuary", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
var monthsAbbrev = [];

for (var i = 0; i < months.length; i++) {
if (months[i].length > 3) {
monthsAbbrev.push(months[i].slice(0, 3));
}
}

console.log(monthsAbbrev);