Javascript中的条件array.join

Question

I have an array of strings and I would like to display them as a comma separated string but add "and" for the last element. For example I have

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

outputs

'Banana, Orange, Apple, Mango'

Is there any way the I add "and" for the last word so it outputs

'Banana, Orange, Apple and Mango'

Answer 1

You can join the first 3 elements of the array using slice and join then append the last element concatenated with 'and'.

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

Answer 2

You may instead use Array.reduce function and implement your own logic, for example:

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

Answer 3

You can try this,

 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); 

Answer 4

Function toSentence of underscore.string has the exact functionality you want. If you don't want to get whole library, you could just borrow 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

You can't pass a function to .join , unfortunately, so you do need to iterate through the loop and join it yourself:

 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) 

You could make a function for this, though:

 // 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']))