What is the most elegant way to insert objects between array elements?
I'm sure there are many ways to achieve that but I'm looking for something "elegant".
a = [
'a',
'b',
'c'
];
magicArrayJoin(a, {value: 255} ); // insert the same object between each item
result == [
'a',
{value: 255},
'b',
{value: 255}
'c'
];
All proposals are welcome. :)
An ordinary loop seems to be the best:
function intersperse(arr, el) {
var res = [], i=0;
if (i < arr.length)
res.push(arr[i++]);
while (i < arr.length)
res.push(el, arr[i++]);
return res;
}
If you're looking for something elegant, it would probably have to use some kind of concatMap , as in
function concatMap(arr, fn) { return [].concat.apply([], arr.map(fn)); }
function intersperse(arr, el) { return concatMap(arr, x => [el, x]).slice(1); }
You can do it with flatMap. It can be found from lodash for example
_.flatMap([1,2,3,4], (value, index, array) =>
array.length -1 !== index // check for the last item
? [value, "s"]
: value
);
ouputs
[1, "s", 2, "s", 3, "s", 4]
In my opinion the most elegant way to do this is the following one:
ES6 syntax version
const insertIntoArray = (arr, value) => {
return arr.reduce((result, element, index, array) => {
result.push(element);
if (index < array.length - 1) {
result.push(value);
}
return result;
}, []);
};
Usage:
insertIntoArray([1, 2, 3], 'x'); // => [1, 'x', 2, 'x', 3]