locutus/esm/haskell/list/intersperse.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function intersperse(separator, items) {
    //  discuss at: https://locutus.io/haskell/list/intersperse/
    // original by: Kevin van Zonneveld (https://kvz.io)
    //      note 1: Inserts separator between elements, like Haskell Data.List.intersperse.
    //   example 1: intersperse(0, [1, 2, 3])
    //   returns 1: [1, 0, 2, 0, 3]
    //   example 2: intersperse('-', ['a'])
    //   returns 2: ['a']
    //   example 3: intersperse(',', [])
    //   returns 3: []
    if (!Array.isArray(items) || items.length === 0) {
        return [];
    }
    const out = [items[0]];
    for (let i = 1; i < items.length; i++) {
        out.push(separator, items[i]);
    }
    return out;
}