feat: convert helper methods

index.js

@@ -23,12 +23,14 @@ const fs = require('./src/helper/fs');
 const obj = require('./src/helper/obj');
 const cmd = require('./src/helper/cmd');
 const is = require('./src/helper/is');
+const convert = require('./src/helper/convert');
 const helper = {
   str,
   fs,
   obj,
   cmd,
-  is
+  is,
+  convert
 };
 
 module.exports = {

package.json

@@ -30,6 +30,7 @@
   },
   "license": "MIT",
   "dependencies": {
+    "big.js": "^6.2.1",
     "clone-deep": "^4.0.1",
     "colors": "1.4.0",
     "enquirer": "^2.3.6",

src/helper/convert.js

@@ -0,0 +1,73 @@
+'use strict';
+
+const is = require('./is');
+const Big = require('big.js');
+
+const defaultDigits = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
+
+/**
+ * co
+ * @param {*} num 
+ * @param {number} from 
+ * @returns {Big}
+ */
+function _convertToDecimalist(num, from) {
+  let len = num.length;
+  let dec = new Big(0);
+  let base = new Big(from);
+  for (let i = 0; i < len; i++) {
+    let pos = defaultDigits.indexOf(num[i]);
+    if (pos === -1) {
+      throw new Error('Invalid number character: ' + num[i]);
+    }
+    dec = base.pow(len - i - 1).times(pos).plus(dec);
+  }
+  return dec;
+}
+
+/**
+ * @param {Big} num 
+ * @param {number} to 
+ * @param {string} digits 
+ * @returns {string}
+ */
+function _convertDecimalist(num, to, digits) {
+  let res = '';
+  let base = new Big(to);
+  while (num.gt(0)) {
+    let mod = num.mod(base);
+    res = digits.charAt(mod) + res;
+    num = num.div(base).round(0, 0);
+  }
+  return res;
+}
+
+/**
+ * @param {number|string} num 
+ * @param {number} from
+ * @param {number} to
+ * @param {{digits:string,patch:string,length?:number}} options 
+ * @returns {string}
+ */
+function _convertNumber(num, from, to, options = {}) {
+  if (to > 62) {
+    throw new Error('target base must be less than 62');
+  }
+  if (!is.string(num)) {
+    num = `${num}`;
+  }
+  const digits = options.digits || defaultDigits;
+  const patch = options.patch || defaultDigits;
+  const { length } = options;
+  let n = from !== 10 ? _convertToDecimalist(num, from) : new Big(num);
+  let res = _convertDecimalist(n, to, digits);
+  if (typeof length !== 'undefined' && res.length < length) {
+    res = patch.charAt(0).repeat(length - res.length) + res;
+  }
+  // console.log({ n, to, digits });
+  return res;
+}
+
+module.exports = {
+  _convertNumber
+};

tests/convert.tests.js

@@ -0,0 +1,22 @@
+'use strict';
+
+const expect = require('chai').expect;
+const _convertNumber = require('../src/helper/convert')._convertNumber;
+
+const digits = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz';
+
+describe('convert test case', function () {
+  it('convert to decimalist', function () {
+    expect(_convertNumber(61, 10, 62)).to.be.equal('Z');
+    expect(_convertNumber(61, 10, 62, { digits })).to.be.equal('z');
+    expect(_convertNumber('z', 62, 10)).to.be.equal('35');
+    expect(_convertNumber('z', 62, 10, { digits })).to.be.equal('DF');
+    expect(_convertNumber('z', 62, 10, { digits, length: 4, patch: '0' })).to.be.equal('00DF');
+    expect(_convertNumber('ZZZZZZ', 62, 10)).to.be.equal('56800235583');
+  });
+
+  it('throw error', function () {
+    expect(() => _convertNumber('$', 62, 10)).to.throw('Invalid number character: $');
+    expect(() => _convertNumber('z', 62, 63)).to.throw('target base must be less than 62');
+  });
+});

tests/fs.tests.js

@@ -129,7 +129,7 @@ describe('fs test case', function () {
     expect(files3.length).to.be.equal(0);
 
     let files4 = await _list(__dirname, false, '.js');
-    expect(files4.length).to.be.equal(10);
+    expect(files4.length).to.be.equal(11);
 
     let files5 = await _list(__dirname + '/not-exist/dir/');
     expect(files5.length).to.be.equal(0);