Pick then flatten a nested array in Javascript -

i want build generic function able extract property object unlimited nested array.

1st example

var jsonobject= {     level1 : [         { id:123, level2 : [                     {id:234, level3 : 'abc'},                     {id:234, level3 : 'cde'}                 ]         },         { id:123, level2 : [                     {id:234, level3 : 'efg'},                     {id:234, level3 : 'ghk'}                 ]         }     ] } 

extractproperty : 'level1.level2.level3' (the function should able support unlimited level depends on this)

expected output (string) : 'abc,cde,efg,ghk'

2nd example

var jsonobject= {     level1 : [         { id:123, level2 : 'abc'},         { id:123, level2 : 'cde'}     ] } 

extractproperty : 'level1.level2'

expected output (string) : 'abc,cde'

here's simple recursive solution 2 examples gave. there edge cases fails though.

const jsonobject = {      level1 : [          { id:123, level2 : [                      {id:234, level3 : 'abc'},                      {id:234, level3 : 'cde'}                  ]          },          { id:123, level2 : [                      {id:234, level3 : 'efg'},                      {id:234, level3 : 'ghk'}                  ]          }      ]  };    function extractproperty(root, path) {      return extractpropertyrecurse(root, path.split("."), 0).join(",");  }    function extractpropertyrecurse(root, levels, index) {      if (array.isarray(root)) {          return [].concat(...root.map(x => extractpropertyrecurse(x, levels, index)));      }            const curr = root && levels[index] && root[levels[index]];      if (curr) {          return extractpropertyrecurse(curr, levels, index + 1)      }            return [root];  }    const results = extractproperty(jsonobject, "level1.level2.level3")  console.log(results);  // out: "abc,cde,efg,ghk"