JSFiddle - React, Tailwind, and code Playground
JavaScript
var elements = [
{ "a": [ "1", "2", ] },
{ "b": [ "1", "2", "3", "4" ] },
{ "c": [ "1", "2", "3", "4", "5", "6" ] }
];
var result = '';
$.each(elements, function(i,e){
$.each(e, function(ind, elem){
$.each(elem, function(index, element){
result += ind + '-' + element + ',';
})
})
})
result = result.substring(0, result.length-1);
console.log(result);