codewars的一道题，搞不懂

Question

题目：Given two arrays of strings a1 and a2 return a sorted array r in lexicographical order of the strings of a1 which are substrings of strings of a2.例子：Example 1:a1 = ["arp", "live", "strong"]a2 = ["lively", "alive", "harp", "sharp", "armstrong"]returns ["arp", "live", "strong"]Example 2:a1 = ["tarp", "mice", "bull"]a2 = ["lively", "alive", "harp", "sharp", "armstrong"]returns []要求：要求实现function inArray(array1,array2){}测试用例：a2 = ["lively", "alive", "harp", "sharp", "armstrong"] a1 = ["xyz", "live", "strong"] Test.assertSimilar(inArray(a1, a2), ["live", "strong"]) a1 = ["live", "strong", "arp"] Test.assertSimilar(inArray(a1, a2), ["arp", "live", "strong"]) a1 = ["tarp", "mice", "bull"] Test.assertSimilar(inArray(a1, a2), [])

Answer 1

供参考：

function inArray(a1, a2){    return a1.filter(el_a1 => a2.find(el_a2 => el_a2.includes(el_a1))).sort();
}