Created
April 20, 2023 05:09
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Custom Base Encoder and Decoder
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| const chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_"; | |
| /** | |
| * Encodes a positive integer to a string using a | |
| * list of unique characters. | |
| * | |
| * @param {number} num - Positive integer | |
| * @returns {string} Encoded string | |
| */ | |
| function encode(num) { | |
| if (isNaN(num)) throw new Error("Not a number"); | |
| if (num<0) throw new Error("Negative integer not supported"); | |
| const base = chars.length; | |
| let result = ''; | |
| let accumulator = num; | |
| do { | |
| const divide = Math.floor(accumulator / base); | |
| const rem = accumulator % base; | |
| result = `${chars.charAt(rem)}${result}`; | |
| if (divide) { | |
| result = `${chars.charAt(divide)}${result}`; | |
| } | |
| accumulator = divide; | |
| } while(accumulator>=base); | |
| return result; | |
| } | |
| /** | |
| * Decodes an encoded string to a positive integer using | |
| * the same list of unique characters used for encoding. | |
| * | |
| * @param {string} str - Encoded string | |
| * @returns {number} Decoded integer | |
| */ | |
| function decode(str) { | |
| const base = chars.length; | |
| const items = `${str}`.split(''); | |
| let num = chars.indexOf(items[0]); | |
| for(let i = 1;i<items.length; i++) { | |
| num = (base * num) + chars.indexOf(items[i]); | |
| } | |
| return num; | |
| } | |
| console.log(encode(240826));//wow | |
| console.log(decode('wow'));//240826 | |
| // (function benchmark(){ | |
| // console.time(); | |
| // for(let i=1;i<=10000;i++) { | |
| // const result = decode(encode(i)); | |
| // if (result !== i) throw new Error("Algo failed"); | |
| // } | |
| // console.timeEnd(); | |
| // // 8.8ms | |
| // })() |
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