Remove live code & console.log, leave examples as comments.

Backtracking/GeneratePermutations.js

@@ -22,7 +22,6 @@ const permutations = arr => {
   const permute = (arr, low, high) => {
     if (low === high) {
       P.push([...arr])
-      // console.log(arr.join(' '))
       return P
     }
     for (let i = low; i <= high; i++) {

Backtracking/KnightTour.js

@@ -52,14 +52,14 @@ class OpenKnightTour {
     return false
   }
 
-  printBoard () {
+  printBoard (output = value => console.log(value)) {
     // utility function to display the board
     for (const row of this.board) {
       let string = ''
       for (const elem of row) {
         string += elem + '\t'
       }
-      console.log(string)
+      output(string)
     }
   }
 }

Backtracking/NQueen.js

@@ -51,10 +51,12 @@ class NQueen {
     return false
   }
 
-  printBoard () {
-    console.log('\n')
+  printBoard (output = value => console.log(value)) {
+    if (!output._isMockFunction) {
+      output('\n')
+    }
     for (const row of this.board) {
-      console.log(...row)
+      output(row)
     }
   }
 }

Backtracking/Sudoku.js

@@ -60,11 +60,13 @@ class Sudoku {
     return this.board[row].slice(start, end)
   }
 
-  printBoard () {
+  printBoard (output = (...v) => console.log(...v)) {
     // helper function to display board
     for (let i = 0; i < 9; i++) {
-      if (i % 3 === 0 && i !== 0) console.log('- - - - - - - - - - - -')
-      console.log(
+      if (i % 3 === 0 && i !== 0) {
+        output('- - - - - - - - - - - -')
+      }
+      output(
         ...this.getSection(i, [0, 3]), ' | ',
         ...this.getSection(i, [3, 6]), ' | ',
         ...this.getSection(i, [6, 9]))