base26.js

base26.js

const { deepStrictEqual } = require("assert");
const table = "ABCDEFGHIJKLMNOPQRSTUVWXWZ";
const tableLength = table.length;

// 13.1
{
  const func1 = row => {
    let result = 0;
    const rowlength = row.length;

    for (let i = 0; i < rowlength; i++) {
      const index = table.indexOf(row[i]) + 1;
      if (index === 0) {
        throw new Error("Invalid row string at" + i);
      }
      result += index * tableLength ** i;
    }
    return result;
  };

  // tests
  const testData = [
    {
      param: "A",
      want: 1,
      wantErr: false
    },
    {
      param: "1",
      want: null,
      wantErr: true
    },
    {
      param: "AA",
      want: 27,
      wantErr: false
    }
  ];

  for (const { param, want, wantErr } of testData) {
    try {
      const got = func1(param);
      deepStrictEqual(got, want, `${param} tests failed`);
      deepStrictEqual(wantErr, false, `${param} wants no error`);
    } catch (e) {
      deepStrictEqual(wantErr, true, `${param} wants error`);
    }
  }

  console.log("13.1 Test successful!");
}

// 13.2
{
  const func2 = x => {
    if (x < 0 || x > 2 ** 32 - 1) {
      return "";
    }
    let result = "";
    let xbt = BigInt(x);
    const base = BigInt(tableLength);
    const one = BigInt(1);
    const zero = BigInt(0);

    while (xbt > zero) {
      const index = xbt % base;
      result = table[index - one] + result;
      xbt /= base;
    }
    return result;
  };

  const testData = [
    {
      param: 1,
      want: "A"
    },
    {
      param: 2,
      want: "B"
    },
    {
      param: 27,
      want: "AA"
    },
    {
      param: -1,
      want: ""
    },
    {
      param: 2 ** 32,
      want: ""
    }
  ];

  for (const { param, want } of testData) {
    deepStrictEqual(func2(param), want, `${param} tests failed`);
  }
  console.log("13.2 Test successful");
}