src/artoo.writers.js
function keysIndex(a) {
    var keys = [],
        l,
        k,
        i;

    for (i = 0, l = a.length; i < l; i++)
      for (k in a[i])
        if (!~keys.indexOf(k))
          keys.push(k);

    return keys;
  }
function keysIndex(a) {
    var keys = [],
        l,
        k,
        i;

    for (i = 0, l = a.length; i < l; i++)
      for (k in a[i])
        if (!~keys.indexOf(k))
          keys.push(k);

    return keys;
  }
function keysIndex ( a ) { var keys = [ ] , l , k , i ; for ( i = 0 , l = a . length ; i < l ; i ++ ) for ( k in a [ i ] ) if ( ! ~ keys . indexOf ( k ) ) keys . push ( k ) ; return keys ; }
Retrieve an index of keys present in an array of objects
Retrieve an index of keys present in an array of objects