有条件的数组.加入Javascript

Question

我有一个字符串数组，我想将它们显示为逗号分隔的字符串，但为最后一个元素添加"and"。例如

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var energy = fruits.join(' ,'); 

输出

'Banana, Orange, Apple, Mango'

有没有办法在最后一个单词后面加上and，输出

'Banana, Orange, Apple and Mango'

Answer 1

您可以使用Array.reduce函数并实现您自己的逻辑，例如:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var energy = fruits.reduce(function (p, d, i) {
  return p + (i === fruits.length - 1 ? ' and ' : ', ') + d;
});

Answer 2

您可以使用slice和join连接数组的前3个元素，然后添加用'and'连接的最后一个元素。

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var energy = fruits.slice(0, fruits.length - 1).join(', '); 
energy += ' and ' + fruits[fruits.length - 1];

Answer 3

你不能传递一个函数给.join，不幸的是，所以你需要通过循环迭代并自己加入它:

const array = ['banana', 'apple', 'taco']
let result = array[0]
for (let i = 1; i < array.length; i++) {
  if (i < array.length - 1) {
    result += ', ' + array[i]
  } else {
    result += ' and ' + array[i]
  }
}
console.log(result)

您可以为此创建一个函数:

// General purpose custom/dynamic join function creator.
function dynamicJoin(fn) {
  return function(array) {
    let result = array[0]
    for (let i = 1; i < array.length; i++) {
      const joiner = fn(array[i - 1], array[i], i, array)
      result += joiner + array[i]
    }
    return result
  }
}
const joinCommaOrAnd = dynamicJoin(function(a, b, i, arr) {
  return (i === arr.length - 1) ? ' and ' : ', '
})
console.log(joinCommaOrAnd(['bread', 'fish', 'butter']))

Answer 4

Function toSentence of underscore。String具有您想要的确切功能。如果你不想要整个图书馆，你可以借toSentence:

function toSentence(array, separator, lastSeparator, serial) {
  separator = separator || ', ';
  lastSeparator = lastSeparator || ' and ';
  var a = array.slice(),
    lastMember = a.pop();
  if (array.length > 2 && serial) lastSeparator = separator + lastSeparator;
  return a.length ? a.join(separator) + lastSeparator + lastMember : lastMember;
};

Answer 5

你可以试试这个，

var delimiter = ', ';
var fruits = ["Banana", "Orange", "Apple", "Mango"];
var energy = fruits.join(delimiter); 
var index = energy.lastIndexOf(delimiter);
energy = energy.substring(0, index) + ' and ' + energy.substring(index + delimiter.length);
console.log(energy);