Node solution for week 88, part 2.

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+//
+// Challenge
+//
+// You are given m x n matrix of positive integers.
+// 
+// Write a script to print spiral matrix as list.
+// 
+
+//
+// We solve this by keeping track of the boundaries (min_x, min_y, max_x,
+// max_y) of the part of the matrix which still needs to be processed.
+// Initially, min_x and min_y are 0, max_x is the index of the bottom row,
+// and max_y is the index of the right most column.
+//
+// We then process the matrix side by side, first going east (top row), 
+// south (left column), west (bottom row), then north (left row). After
+// doing a side, we update the corresponding min/max value. That is,
+// after doing the top row, we increment min_x; right column, decrement
+// max_y; bottom row, decrement max_x; left column, increment min_y.
+//
+// We're done when min_x > max_x, or min_y > max_y.
+//
+
+//
+// Read STDIN. Split on newlines, then on white space.
+//
+let matrix = require      ("fs")
+           . readFileSync (0)                       // Read all.
+           . toString     ()                        // Turn it into a string.
+           . split        ("\n")                    // Split on newlines.
+           . filter       (_ => _ . length)         // Filter empty lines.
+           . map          (_ => _ . trim ()         // Trim white space.
+                                 . split (/\s+/))  // Split on whitespace.
+;
+
+//
+// Check if all rows are the same length
+//
+matrix . forEach (row => {
+    if (row . length != matrix [0] . length) {
+        throw "Not all rows are of equal length";
+    }
+});
+
+
+let EAST      = 0;
+let SOUTH     = 1;
+let WEST      = 2;
+let NORTH     = 3;
+
+let direction = EAST;  // Initial direction
+
+let min_x     = 0;
+let max_x     = matrix     . length - 1;
+let min_y     = 0;
+let max_y     = matrix [0] . length - 1;
+
+
+let output = "";
+while (min_x <= max_x && min_y <= max_y) {
+    if (direction == EAST) {
+        for (let y = min_y; y <= max_y; y ++) {
+            output = output + ", " + matrix [min_x] [y];
+        }
+        min_x ++;
+    }
+    if (direction == SOUTH) {
+        for (let x = min_x; x <= max_x; x ++) {
+            output = output + ", " + matrix [x] [max_y];
+        }
+        max_y --;
+    }
+    if (direction == WEST) {
+        for (let y = max_y; y >= min_y; y --) {
+            output = output + ", " + matrix [max_x] [y];
+        }
+        max_x --;
+    }
+    if (direction == NORTH) {
+        for (let x = max_x; x >= min_x; x --) {
+            output = output + ", " + matrix [x] [min_y];
+        }
+        min_y ++;
+    }
+
+    direction = (direction + 1) % (NORTH + 1);
+}
+
+//
+// Remove leading ", " and print result
+//
+process . stdout . write (output . slice (2) + "\n");