forloop_rollyourown_ex.js

// Single for loop (i)
// i loop
loop(0, function(i){return i<10;}, function(i){return i+1;},
  function(i, next){
    // looping.
    console.log(i);
    next();
  },
  function(i){ console.log("all done."); }
);

// 2-Level deep for loop (i,j)
// i loop
loop(0, function(i){return i<10;}, function(i){return i+1;},
  function(i, next){
    // j loop
    loop(0, function(j){return j<10;}, function(j){return j+1;},
      function(j, next){
        // looping.
        console.log(i,j);
        next();
      },
      function(i){ next(); } // note: this next is the parent's next. yay!
    );
  },
  function(i){ console.log("all done."); }
);

// 4-Level deep for loop (i,j,k,m)
// i loop
loop(0, function(i){return i<5;}, function(i){return i+1;},
  function(i, next){
    // j loop
    loop(0, function(j){return j<5;}, function(j){return j+1;},
      function(j, next){
        // k loop
        loop(0, function(k){return k<5;}, function(k){return k+1;},
          function(k, next){
            // m loop
            loop(0, function(m){return m<5;}, function(m){return m+1;},
              function(m, next){
                // --
                // looping.
                console.log(i,j,k,m);
                next();
                // --
              },
              function(m){ next(); } // note: parent's next.
            );
          },
          function(k){ next(); } // note: parent's next.
        );
      },
      function(j){ next(); } // note: this next is the parent's.
    );
  },
  function(i){ console.log("all done."); }
);