将数组缩减为单个字符串

Question

我想使用 reduce 函数而不是这样做:

var result = '';
authors.forEach(
    function(author) {
        result += author.name + ', ';
    }
);
console.log(result);

所以在数组authors中有几个名字。现在我想用这个名称构建一个字符串，用逗号分隔（最后一个除外）。

var result = authors.reduce(function (author, index) {
    return author + ' ';
}, '');
console.log(result);

Answer 1

您正在重塑 join()

var authors = ["a","b","c"];
var str = authors.join(", ");
console.log(str);

如果你想使用 reduce 添加一个 if 检查

var authors = ["a","b","c"];

var result = authors.reduce(function (author, val, index) {
    var comma = author.length ? ", " : "";
    return author + comma + val;
}, '');
console.log(result);

因为我错过了映射部分来让人们开心...

var authors = [{
  name: "a"
}, {
  name: "b"
}, {
  name: "c"
}];

var res = authors.map( function(val) { return val.name; }).join(", ");
console.log(res);

或

var authors = [{
  name: "a"
}, {
  name: "b"
}, {
  name: "c"
}];
var result = authors.reduce(function(author, val, index) {
  var comma = author.length ? ", " : "";
  return author + comma + val.name;
}, '');
console.log(result);

Answer 2

试试这个：

var authors = ["Mikel", "Brad", "Jessy", "Pof", "MArting"]
var result = authors.reduce( (prev, curr) => prev +', '+ curr )

console.log(result)

Answer 3

对，所以它是一个对象。让我们先映射名称：

var result = authors.map(function( author ) {
    return author.name;
}).join(', ');

Answer 4

刚刚收到了一堆答案，这里还有一个！

第一个选项是使用本机 js join 方法，它消除了 reduce 的需要。 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/join

var authors = ['some author', 'another author', 'last author'];
var authorString = authors.join(",");
console.log(authorString);

重要 - 如果你的数组包含对象，那么你可能想在加入之前映射它：

var authors = [{name: 'some author'},{name: 'another author'},{name: 'last author'}]
var authorString = authors.map(function(author){
    return author.name;
}).join(",");
console.log(authorString);

或者，如果您真的热衷于使用 reduce，只需确保在传入回调时使用之前的值、当前值和索引即可。 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

var authorString = authors.reduce(function(prevVal,currVal,idx){
    return idx == 0 ? currVal : prevVal + ', ' + currVal;
}, '')
console.log(authorString);

重要 - 同样，如果您的数组包含对象，那么您需要确保您使用的是 'name property':

var authors = [{name: 'some author'},{name: 'another author'},{name: 'last author'}];
var authorString = authors.reduce(function(prevVal,currVal,idx){
    return idx == 0 ? currVal.name : prevVal + ', ' + currVal.name;
}, '')
console.log(authorString);

Answer 5

我也遇到过这个。这些答案中的大多数都没有考虑到您想要 authors 名称，这意味着您有一个对象数组。

一行解决方案：

authors.reduce((prev, curr) => [...prev, curr.name], []).join(', ');

将数组缩减为单个字符串

Reduce array to a single string

javascript

underscore.js