javascript 有没有办法在js数组中加入元素，但让最后一个分隔符不同？
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Is there a way to join the elements in an js array, but let the last separator be different?
提问by Eivind Eidheim Elseth
What I want is something like Array.join(separator), but which takes a second argument Array.join(separator, beforeLastElement), so when I say [foo, bar, baz].join(", ", " or")I would get "foo, bar or baz". I guess I could write a function that used Array.sliceto separate out the last element, but is there some well known method that I could use instead?
我想要的是类似的东西Array.join(separator)，但这需要第二个参数Array.join(separator, beforeLastElement)，所以当我说[foo, bar, baz].join(", ", " or")我会得到"foo, bar or baz". 我想我可以编写一个用于Array.slice分离最后一个元素的函数，但是有没有一些众所周知的方法可以代替？
采纳答案by Justin Ethier
No, this is specific enough that you will have to write a custom function. The good news is, as you said, once you use Array.jointo take care of all the separators, the last one will be easy enough to update.
不，这足够具体，您必须编写自定义函数。好消息是，正如您所说，一旦您使用Array.join了所有分隔符，最后一个将很容易更新。
回答by Denys Séguret
There's no predefined function, because it's quite simple.
没有预定义的函数，因为它非常简单。
var a = ['a', 'b', 'c'];
var str = a.slice(0, -1).join(',')+' or '+a.slice(-1);
There's also a specification problem for the main use case of such a function which is natural language formatting. For example if we were to use the Oxford comma logic we would have a different result than what you're looking for:
这种函数的主要用例也存在规范问题，即自然语言格式。例如，如果我们要使用牛津逗号逻辑，我们将得到与您要查找的结果不同的结果：
// make a list in the Oxford comma style (eg "a, b, c, and d")
// Examples with conjunction "and":
// ["a"] -> "a"
// ["a", "b"] -> "a and b"
// ["a", "b", "c"] -> "a, b, and c"
exports.oxford = function(arr, conjunction, ifempty){
let l = arr.length;
if (!l) return ifempty;
if (l<2) return arr[0];
if (l<3) return arr.join(` ${conjunction} `);
arr = arr.slice();
arr[l-1] = `${conjunction} ${arr[l-1]}`;
return arr.join(", ");
}
So it seems better to let this problem in userland.
所以把这个问题放在用户空间似乎更好。
回答by Joseph
May I suggest:
我可以建议：
['tom', 'dick', 'harry'].join(', ').replace(/, ([^,]*)$/, ' and ')
> "tom, dick and harry"
回答by CBarr
Building off of @dystroy's answer:
基于@dystroy 的回答：
function formatArray(arr){
var outStr = "";
if (arr.length === 1) {
outStr = arr[0];
} else if (arr.length === 2) {
//joins all with "and" but no commas
//example: "bob and sam"
outStr = arr.join(' and ');
} else if (arr.length > 2) {
//joins all with commas, but last one gets ", and" (oxford comma!)
//example: "bob, joe, and sam"
outStr = arr.slice(0, -1).join(', ') + ', and ' + arr.slice(-1);
}
return outStr;
}
Example usages:
示例用法：
formatArray([]); //""
formatArray(["a"]); //"a"
formatArray(["a","b"]); //"a and b"
formatArray(["a","b","c"]); //"a, b, and c"
formatArray(["a","b","c","d"]); //"a, b, c, and d"
回答by Charlie Wynn
Array.prototype.join2 = function(all, last) {
var arr = this.slice(); //make a copy so we don't mess with the original
var lastItem = arr.splice(-1); //strip out the last element
arr = arr.length ? [arr.join(all)] : []; //make an array with the non-last elements joined with our 'all' string, or make an empty array
arr.push(lastItem); //add last item back so we should have ["some string with first stuff split by 'all'", last item]; or we'll just have [lastItem] if there was only one item, or we'll have [] if there was nothing in the original array
return arr.join(last); //now we join the array with 'last'
}
> [1,2,3,4].join2(', ', ' and ');
>> "1, 2, 3 and 4"
回答by Pawe?
there is a package join-array
有一个包join-array
const join = require('join-array');
const names = ['Rachel','Taylor','Julia','Robert','Jasmine','Lily','Madison'];
const config = {
array: names,
separator: ', ',
last: ' and ',
max: 4,
maxMessage:(missed)=>`(${missed} more...)`
};
const list = join(config); //Rachel, Taylor, Julia, (3 more...) and Madison
回答by Vignesh Raja
Though its a late answer, adding some approaches.
虽然它是一个迟到的答案，但添加了一些方法。
Method 1: Using Array.splice() add the last delimiterbefore last element and join and remove the last two ,.
方法 1：使用 Array.splice() 添加last delimiter前最后一个元素并连接和删除最后两个,。
function join(arr,last)
{
if(!Array.isArray(arr)) throw "Passed value is not of array type.";
last = last || ' and '; //set 'and' as default
(arr.length>1 && arr.splice(-1,0,last));
arr = arr.join().split("");
arr[arr.lastIndexOf(",")]="";
arr[arr.lastIndexOf(",")]="";
return arr.join("");
}
console.log( join([1]) ); //single valued array
console.log( join([1,2]) ); //double valued array
console.log( join([1,2,3]) ); //more than 2 values array,
console.log( join([1,2,3],' or ') ); //with custom last delimiter
console.log( join("name") ); //Non-array typeMethod 2: Using Array.reduce() to construct the string by traversing each element.
方法二：使用Array.reduce()遍历每个元素来构造字符串。
function join(arr,last)
{
if(!Array.isArray(arr)) throw "Passed value is not of array type.";
last=last||' and ';
return arr.reduce(function(acc,value,index){
if(arr.length<2) return arr.join();
return acc + (index>=arr.length-2 ? index>arr.length-2 ? value : value+last : value+",");
},"");
}
console.log( join([1]) ); //single valued array
console.log( join([1,2]) ); //double valued array
console.log( join([1,2,3]) ); //more than 2 values array,
console.log( join([1,2,3,4],' or ') ); //with custom last delimiter
console.log( join("name") ); //Non-array type回答by Yair Levy
compact version :)
紧凑版:)
function customJoin(arr,s1,s2){
return(arr.slice(0,-1).join(s1).concat(arr.length > 1 ? s2 : '', arr.slice(-1)));
}
/*
arr: data array
s1: regular seperator (string)
s2: last seperator (string)
*/
function customJoin(arr,s1,s2){
return(arr.slice(0,-1).join(s1).concat(arr.length > 1 ? s2 : '', arr.slice(-1)));
}
let arr1 = ['a','b','c','d'];
let arr2 = ['singleToken'];
console.log(customJoin(arr1,',',' and '));
//expected: 'a,b,c and d'
console.log(customJoin(arr1,'::',' and finally::'));
//expected: 'a::b::c and finally::d'
console.log(customJoin(arr2,',','and '));
//expected: 'singleToken'回答by abagmut
For me the simplest solution is:
对我来说，最简单的解决方案是：
['1', '2', '3'].reduce((previous, current, index, array) => {
if (index === array.length - 1) {
return previous + ' & ' + current;
} else {
return previous + ', ' + current;
}
})
回答by Maxime Lechevallier
In-line solution using reduce:
使用 reduce 的在线解决方案：
[1, 2, 3, 4, 5].reduce((text, value, i, array) => text + (i < array.length - 1 ? ', ' : ' or ') + value);
=> 1, 2, 3, 4 or 5"
