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| function railFenceCipher(operation, string, height = 3) { | |
| function performOperation(operation, string, height, lines) { | |
| let results = ''; // only for decrypt | |
| let currentLine = 0; | |
| let moveUp = true; | |
| let moveDown = false; | |
| for (let i = 0; i < lines[0].length; i += 1) { | |
| if (operation === 'encrypt') { | |
| lines[currentLine].splice(i, 1, string[i]); | |
| } else if (operation === 'decrypt') { | |
| results += lines[currentLine][i]; | |
| } | |
| if ((moveUp && currentLine + 1 > height - 1) || | |
| (moveDown && currentLine - 1 < 0)) { | |
| if (moveUp) currentLine -= 1; | |
| if (moveDown) currentLine += 1; | |
| moveUp = !moveUp; | |
| moveDown = !moveDown; | |
| } else if (moveUp) { | |
| currentLine += 1; | |
| } else if (moveDown) { | |
| currentLine -= 1; | |
| } | |
| } | |
| if (operation === 'encrypt') { | |
| return lines.reduce((str, line) => str += line.join(' ') + '\n', ''); | |
| } else if (operation === 'decrypt') { | |
| return results; | |
| } | |
| } | |
| if (operation === 'encrypt' && height === 1) { | |
| return 'Height must be 2 or more.'; | |
| } | |
| if (operation === 'encrypt') { | |
| string = string.replace(/\W/g, ''); | |
| lines = [...Array(height)].map((_, i) => i) | |
| .map(line => [...Array(string.length)].map((_, i) => i)) | |
| .map(line => line.map(element => '.')); | |
| } else if (operation === 'decrypt') { | |
| string = string.replace(/\n$/, ''); | |
| lines = string.split('\n').map(line => line.split(' ')); | |
| height = lines.length; | |
| } | |
| return performOperation(operation, string, height, lines); | |
| } | |
| // each lines ends with \n | |
| cipher = 'W . . . E . . . C . . . R . . . L . . . T . . . E\n. E . R . D . S . O . E . E . F . E . A . O . C .\n. . A . . . I . . . V . . . D . . . E . . . N . .\n'; | |
| console.log(railFenceCipher('decrypt', cipher)); | |
| // last line doesn't end with \n | |
| cipher = 'W . . . E . . . C . . . R . . . L . . . T . . . E\n. E . R . D . S . O . E . E . F . E . A . O . C .\n. . A . . . I . . . V . . . D . . . E . . . N . .'; | |
| console.log(railFenceCipher('decrypt', cipher)); | |
| // only print letters | |
| message = 'WE ARE DISCOVERED FLEE AT ONCE'; | |
| console.log(railFenceCipher('encrypt', message, 3)); | |
| // only encrypts print letters | |
| message = 'WE @#$ARE DISCOVERED -----FLEE ~~~AT ^&*(ONCE'; | |
| console.log(railFenceCipher('encrypt', message, 5)); | |
| // works with no height (3 is default) | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message)); | |
| // doesn't work with height 1 | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message, 1)); | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message, 2)); | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message, 3)); | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message, 4)); | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message, 10)); | |
| message = 'I LOVE LAUNCH SCHOOL'; | |
| console.log(railFenceCipher('encrypt', message, 20)); |
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