Rendering comma separated list of links - reactjs

Question

I'm trying to output a list of comma separated links and this is my solution.
var Item = React.createComponent({
render: function() {
var tags = [],
tag;
for (var i = 0, l = item.tags.length; i < l; i++) {
if (i === item.tags.length - 1) {
tag = <span><Tag key={i} tag={item.tags[i]} /></span>;
} else {
tag = <span><Tag key={i} tag={item.tags[i]} /><span>, </span></span>;
}
tags.push(tag);
}
return (
<tr>
<td>
{item.name}
</td>
<td>
{tags}
</td>
</tr>
);
}
});
I was just wondering if there was a better, more clean way to accomplish this?
Thanks

Answer 1

Simply
{tags.map((tag, i) => <span key={i}>
{i > 0 && ", "}
<Tag tag={tag} />
</span>)}
In React 16 it can be done even more simpler:
{tags.map((tag, i) => [
i > 0 && ", ",
<Tag key={i} tag={tag} />
])}

Answer 2

At Khan Academy we use a helper called intersperse for this:
/* intersperse: Return an array with the separator interspersed between
* each element of the input array.
*
* > _([1,2,3]).intersperse(0)
* [1,0,2,0,3]
*/
function intersperse(arr, sep) {
if (arr.length === 0) {
return [];
}
return arr.slice(1).reduce(function(xs, x, i) {
return xs.concat([sep, x]);
}, [arr[0]]);
}
which allows you to write code like:
var tags = item.tags.map(function(tag, i) {
return <Tag key={i} tag={item.tags[i]} />;
};
tags = intersperse(tags, ", ");

Answer 3

Or simply write the list items to an unordered list and use CSS.
var Item = React.createComponent({
render: function() {
var tags = this.props.item.tags.map(function(i, item) {
return <li><Tag key={i} tag={item} /></li>
});
return (
<tr>
<td>
{this.props.item.name}
</td>
<td>
<ul className="list--tags">
{tags}
</ul>
</td>
</tr>
);
}
});
And the CSS:
.list--tags {
padding-left: 0;
text-transform: capitalize;
}
.list--tags > li {
display: inline;
}
.list--tags > li:before {
content:',\0000a0'; /* Non-breaking space */
}
.list--tags > li:first-child:before {
content: normal;
}

Answer 4

import React from 'react';
import { compact } from 'lodash';
// Whatever you want to separate your items with commas, space, border...
const Separator = () => { ... };
// Helpful component to wrap items that should be separated
const WithSeparators = ({ children, ...props }) => {
// _.compact will remove falsey values: useful when doing conditional rendering
const array = compact(React.Children.toArray(children));
return array.map((childrenItem, i) => (
<React.Fragment key={`${i}`}>
{i > 0 && <Separator {...props} />}
{childrenItem}
</React.Fragment>
));
};
const MyPage = () => (
<WithSeparators/>
<div>First</div>
{second && (<div>Maybe second</div>)}
{third && (<div>Maybe third</div>)}
<div>Fourth</div>
</WithSeparators>
);

Answer 5

A function component that does the trick. Inspired by #imos's response. Works for React 16.
const Separate = ({ items, render, separator = ', ' }) =>
items.map((item, index) =>
[index > 0 && separator, render(item)]
)
<Separate
items={['Foo', 'Bar']}
render={item => <Tag tag={item} />}
/>

Answer 6

Here's a solution that allows <span>s and <br>s and junk as the separator:
const createFragment = require('react-addons-create-fragment');
function joinElements(arr,sep=<br/>) {
let frag = {};
for(let i=0,add=false;;++i) {
if(add) {
frag[`sep-${i}`] = sep;
}
if(i >= arr.length) {
break;
}
if(add = !!arr[i]) {
frag[`el-${i}`] = arr[i];
}
}
return createFragment(frag);
}
It filters out falsey array elements too. I used this for formatting addresses, where some address fields are not filled out.
It uses fragments to avoid the warnings about missing keys.

Answer 7

Simple one:
{items.map((item, index) => (
<span key={item.id}>
{item.id}
{index < items.length - 1 && ', '}
</span>
))}

Answer 8

To add to the great answers above Ramda has intersperse.
To comma separate a bunch of items you could do:
const makeLinks = (x: Result[]) =>
intersperse(<>,</>, map(makeLink, x))
Pretty succinct

Answer 9

The solution without extra tags
<p className="conceps inline list">
{lesson.concepts.flatMap((concept, i) =>
[concept, <span key={i} className="separator">•</span>]
, ).slice(-1)}
</p>
generates something like
Function • Function type • Higher-order function • Partial application

Answer 10

The easiest way to do
const elementsArr = ["a", "b", "c"];
let elementsToRender = [] ;
elementsArr.forEach((element, index) => {
let elementComponent = <TAG className="abc" key={element.id}>{element}</TAG>
elementsToRender.push(elementComponent);
if(index !== (elementsArr.length - 1)){
elementsToRender.push(", ");
}
});
render(){
return (
<div>{elementsToRender}</div>
)
}