fix token method and added powerset method

Author: suryapratapsinghsuryavanshi

README.md

@@ -30,7 +30,7 @@
 [![Windows Build][appveyor-image]][appveyor-url]
 [![Test Coverage][coveralls-image]][coveralls-url]
 
-[npm-image]: https://img.shields.io/badge/npm-v3.30.15-blue
+[npm-image]: https://img.shields.io/badge/npm-v3.31.15-blue
 [npm-url]: https://www.npmjs.com/package/solverjs
 [downloads-image]: https://img.shields.io/badge/Downloads-200%2FWeeks-green
 [downloads-url]: https://www.npmjs.com/package/solverjs
@@ -383,6 +383,12 @@ The min method returns the minimum value from the given array.
     console.log(solverjs.min([2, 5, 6, 3]));
     // The output is : 2
 
+### getPowerset
+In mathematics, the power set (or powerset) of a set S is the set of all subsets of S, including the empty set and S itself.
+
+    console.log(solverjs.getPowerset([1, 2, 3]));
+    // The output is : [[], [ 1 ], [ 2 ], [ 1, 2 ], [ 3 ], [ 1, 3 ], [ 2, 3 ], [ 1, 2, 3 ]]
+
 ## Number System Conversion
 We all know we have very frequently is number system conversion in programming, our number system conversion methods provide all type of conversion of the numbers systems.
 

index.js

@@ -220,7 +220,8 @@ let {
     remainder,
     isFibonacci,
     max,
-    min
+    min,
+    getPowerset
 } = require('./src/math/math');
 
 // numbers systems.
@@ -581,6 +582,7 @@ module.exports = {
     isFibonacci,
     max,
     min,
+    getPowerset,
     // numbers system.
     hexToDec,
     hexToOct,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "solverjs",
-  "version": "3.30.15",
+  "version": "3.31.15",
   "description": "This package is a combination of many useful functions.",
   "main": "index.js",
   "scripts": {
@@ -40,6 +40,7 @@
     "lcm",
     "hcf",
     "ascii",
+    "getPowerset",
     "reverse",
     "isPalindrome",
     "permutation",

src/math/math.js

@@ -433,7 +433,7 @@ let isTitle = (str) => /^([A-Z][a-z]+)$/.test(str);
 
 // unique token generator, generate a unique token.
 /**
- * Fenerate a unique token, every time you run without any arguments.
+ * The token method generates and returns a unique token in string format, every time you run without any arguments.
  * @returns return a unique token every time to run.
  */
 let token = () => {
@@ -514,6 +514,24 @@ let max = (arr) => {
     return mn;
 }
 
+/**
+ * The getPowerset method calculates all subset of the given set and return it, also known as powerset.
+ * @param {Array} set A set array.
+ * @returns {Array[][]} `Powerset` Returns the powerset of the given set.
+ */
+function getPowerset(set) {
+    let subset = [[]];
+
+    for(let ele of set) {
+        let len = subset.length;
+        for(let i = 0; i < len; i++) {
+            subset.push([...subset[i], ele]);
+        }
+    }
+
+    return subset;
+}
+
 // export maths methods.
 module.exports = {
     getFib,
@@ -555,5 +573,6 @@ module.exports = {
     remainder,
     isFibonacci,
     max,
-    min
+    min,
+    getPowerset
 }