“The convoluted converter”

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try {
  if (process.argv.length === 4) {
    const target = process.argv[2];
    const input = process.argv[3];
    if (target === "-bin" || target === "-hex" || target === "-dec") {
      if (/^(0b[01]+|0x[0-9a-fA-F]+|0|[1-9]\d*)$/.test(input)) {
        let decimal;
        const prefix = input.substr(0, 2);
        if (prefix === "0b") decimal = parseInt(input.substr(2), 2);
        else if (prefix === "0x") decimal = parseInt(input.substr(2), 16);
        else decimal = parseInt(input);
        if (target === "-bin") console.log("0b" + decimal.toString(2));
        else if (target === "-hex") console.log("0x" + decimal.toString(16));
        else console.log(decimal.toString());
      } else {
        throw "Input number invalid";
      }
    } else {
      throw "Target option invalid";
    }
  } else {
    throw "Wrong number of arguments";
  }
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#1. Divide and conquer

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const convert = (target, input) => {
  let decimal;
  const prefix = input.substr(0, 2);
  if (prefix === "0b") decimal = parseInt(input.substr(2), 2);
  else if (prefix === "0x") decimal = parseInt(input.substr(2), 16);
  else decimal = parseInt(input);
  if (target === "-bin") return "0b" + decimal.toString(2);
  else if (target === "-hex") return "0x" + decimal.toString(16);
  else return decimal.toString();
};

const options = ["-bin", "-hex", "-dec"];
const inputShape = /^(0b[01]+|0x[0-9a-fA-F]+|0|[1-9]\d*)$/;

try {
  if (process.argv.length === 4) {
    const target = process.argv[2];
    const input = process.argv[3];
    if (options.includes(target)) {
      if (inputShape.test(input)) {
        const result = convert(target, input);
        console.log(result);
      } else {
        throw "Input number invalid";
      }
    } else {
      throw "Target option invalid";
    }
  } else {
    throw "Wrong number of arguments";
  }
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#2. Maximise cohesion

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const convert = (target, input) => {
  let decimal;
  const prefix = input.substr(0, 2);
  if (prefix === "0b") decimal = parseInt(input.substr(2), 2);
  else if (prefix === "0x") decimal = parseInt(input.substr(2), 16);
  else decimal = parseInt(input);
  if (target === "-bin") return "0b" + decimal.toString(2);
  else if (target === "-hex") return "0x" + decimal.toString(16);
  else return decimal.toString();
};

const options = ["-bin", "-hex", "-dec"];
const inputShape = /^(0b[01]+|0x[0-9a-fA-F]+|0|[1-9]\d*)$/;

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  if (!options.includes(target)) {
    throw "Target option invalid";
  }
  const input = process.argv[3];
  if (!inputShape.test(input)) {
    throw "Input number invalid";
  }
  const result = convert(target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#3. Schödinger variables

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const toDecimal = (input) => {
  switch(input.substr(0, 2)) {
    case "0b": return parseInt(input.substr(2), 2);
    case "0x": return parseInt(input.substr(2), 16);
  }
  return parseInt(input);
};

const convert = (target, input) => {
  const decimal = toDecimal(input);
  if (target === "-bin") return "0b" + decimal.toString(2);
  else if (target === "-hex") return "0x" + decimal.toString(16);
  else return decimal.toString();
};

const options = ["-bin", "-hex", "-dec"];
const inputShape = /^(0b[01]+|0x[0-9a-fA-F]+|0|[1-9]\d*)$/;

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  if (!options.includes(target)) {
    throw "Target option invalid";
  }
  const input = process.argv[3];
  if (!inputShape.test(input)) {
    throw "Input number invalid";
  }
  const result = convert(target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#4. Conditional complexity

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const targetConverters = {
  "-bin": d => "0b" + d.toString(2),
  "-hex": d => "0x" + d.toString(16),
  "-dec": d => d.toString(),
};

const inputConverters = {
  "0b": i => parseInt(i.substr(2), 2),
  "0x": i => parseInt(i.substr(2), 16),
  "": i => parseInt(i)
};

const convert = (target, input) => {
  const toDecimal = inputConverters[input.substr(0, 2)] || inputConverters[""];
  const decimal = toDecimal(input);
  return targetConverters[target](decimal);
};

const options = ["-bin", "-hex", "-dec"];
const inputShape = /^(0b[01]+|0x[0-9a-fA-F]+|0|[1-9]\d*)$/;

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  if (!options.includes(target)) {
    throw "Target option invalid";
  }
  const input = process.argv[3];
  if (!inputShape.test(input)) {
    throw "Input number invalid";
  }
  const result = convert(target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#5. Don’t repeat yourself

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const converters = {
  "-bin": {base: 2, prefix: "0b"},
  "-hex": {base: 16, prefix: "0x"},
  "-dec": {base: 10, prefix: ""},
};

const convert = (target, input) => {
  const inputConverter = Object.values(converters)
    .find(c => c.prefix === input.substr(0, 2)) || converters["-dec"];
  const decimal = parseInt(
    input.substr(inputConverter.prefix.length),
    inputConverter.base
  );
  const targetConverter = converters[target];
  return targetConverter.prefix + decimal.toString(targetConverter.base);
};

const inputShape = /^(0b[01]+|0x[0-9a-fA-F]+|0|[1-9]\d*)$/;

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  if (!Object.keys(converters).includes(target)) {
    throw "Target option invalid";
  }
  const input = process.argv[3];
  if (!inputShape.test(input)) {
    throw "Input number invalid";
  }
  const result = convert(target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#6. Open-closed principle

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const converters = {
  "-bin": {prefix: "0b", base: 2, shape: /^0b[01]+$/},
  "-hex": {prefix: "0x", base: 16, shape: /^0x[0-9a-fA-F]+$/},
  "-dec": {prefix: "", base: 10, shape: /^(0|[1-9]\d*)$/},
};

const convert = (inputConverter, target, input) => {
  const decimal = parseInt(
    input.substr(inputConverter.prefix.length),
    inputConverter.base
  );
  const targetConverter = converters[target];
  return targetConverter.prefix + decimal.toString(targetConverter.base);
};

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  if (!Object.keys(converters).includes(target)) {
    throw "Target option invalid";
  }
  const input = process.argv[3];
  const inputConverter = Object.values(converters).find(p => p.shape.test(input));
  if (!inputConverter) {
    throw "Input number invalid";
  }
  const result = convert(inputConverter, target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#7. Separation of concerns

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const converters = {
  "-bin": {prefix: "0b", base: 2, shape: /^0b[01]+$/},
  "-hex": {prefix: "0x", base: 16, shape: /^0x[0-9a-fA-F]+$/},
  "-dec": {prefix: "", base: 10, shape: /^(0|[1-9]\d*)$/},
};

const convert = (target, input) => {
  const inputConverter = Object.values(converters).find(p => p.shape.test(input));
  if (!inputConverter) {
    throw "Input number invalid";
  }
  const targetConverter = converters[target];
  if (!targetConverter) {
    throw "Target option invalid";
  }
  const decimal = parseInt(
    input.substr(inputConverter.prefix.length),
    inputConverter.base
  );
  return targetConverter.prefix + decimal.toString(targetConverter.base);
};

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  const input = process.argv[3];
  const result = convert(target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#8. Hello again, Schrödinger variables

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const converters = {
  "-bin": {prefix: "0b", base: 2, shape: /^0b[01]+$/},
  "-hex": {prefix: "0x", base: 16, shape: /^0x[0-9a-fA-F]+$/},
  "-dec": {prefix: "", base: 10, shape: /^(0|[1-9]\d*)$/},
};

const convert = (target, input) => {
  const inputConverter = Object.values(converters).find(p => p.shape.test(input))
    || (() => {throw "Input number invalid"})();
  const targetConverter = converters[target]
    || (() => {throw "Target option invalid"})();
  const decimal = parseInt(
    input.substr(inputConverter.prefix.length),
    inputConverter.base
  );
  return targetConverter.prefix + decimal.toString(targetConverter.base);
};

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const target = process.argv[2];
  const input = process.argv[3];
  const result = convert(target, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#9. Make the domain model shine

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const numberSystems = [
  {name: "bin", prefix: "0b", base: 2, shape: /^0b[01]+$/},
  {name: "hex", prefix: "0x", base: 16, shape: /^0x[0-9a-fA-F]+$/},
  {name: "dec", prefix: "", base: 10, shape: /^(0|[1-9]\d*)$/},
];

const convert = (targetName, input) => {
  const inputNS = numberSystems.find(n => n.shape.test(input))
    || (() => {throw "Input number invalid"})();
  const targetNS = numberSystems.find(n => n.name === targetName)
    || (() => {throw "Target option invalid"})();
  const intermediate = parseInt(
    input.substr(inputNS.prefix.length),
    inputNS.base
  );
  return targetNS.prefix + intermediate.toString(targetNS.base);
};

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const targetName = process.argv[2].substr(1);
  const input = process.argv[3];
  const result = convert(targetName, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}

#10. Single level of abstraction

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const numberSystems = [
  {name: "bin", prefix: "0b", base: 2, shape: /^0b[01]+$/},
  {name: "hex", prefix: "0x", base: 16, shape: /^0x[0-9a-fA-F]+$/},
  {name: "dec", prefix: "", base: 10, shape: /^(0|[1-9]\d*)$/},
];

const normalise = (ns, input) => parseInt(input.substr(ns.prefix.length), ns.base);
const translate = (ns, intermediate) => ns.prefix + intermediate.toString(ns.base);
const convert = (targetName, input) => {
  const inputNS = numberSystems.find(n => n.shape.test(input))
    || (() => {throw "Input number invalid"})();
  const targetNS = numberSystems.find(n => n.name === targetName)
    || (() => {throw "Target option invalid"})();
  const intermediate = normalise(inputNS, input);
  return translate(targetNS, intermediate);
};

try {
  if (process.argv.length !== 4) {
    throw "Wrong number of arguments";
  }
  const targetName = process.argv[2].substr(1);
  const input = process.argv[3];
  const result = convert(targetName, input);
  console.log(result);
} catch (e) {
  console.log("Error: " + e);
  process.exit(1);
}