JavaScript數組查找是否包含某些字符串

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.

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 []

my answer：

function inArray(array1,array2){
    var array3 = [];
   for(var i = 0 ; i <array1.length ; i++){
     var pattern = RegExp(array1[i]);
     if(pattern.test(array2) ==true && array1[i]!==undefined)
        array3.push(array1[i])
   }
   return array3.sort();
}

測試用
var a2 = ["lively", "alive", "harp", "sharp", "armstrong"]
var a1 = ["xyz", "live", "strong"]
console.log(inArray(a1, a2));   
//["live", "strong"])

var a1 = ["live", "strong", "arp"]
console.log(inArray(a1, a2));    
//["arp", "live", "strong"])

var a1 = ["tarp", "mice", "bull"]
console.log(inArray(a1, a2));   
// []

best answer：

arr.filter()檢測數值元素，並返回符合條件全部元素的數組。

arr.join()把數組的全部元素放入一個字符串

arr.indexOf()搜索數組中的元素，並返回它所在的位置。

function inArray(array1,array2){
    return array1.filter(function(value){return (array2.join('-').indexOf(value))!=-1}).sort();
}