使用JavaScript实现一个简单的编译器_javascript进阶

function tokenizer(input) {
  let current = 0;
  const tokens = [];

  while (current < input.length) {
    let char = input[current];

    // 处理括号
    if (char === '(') {
      tokens.push({ type: 'paren', value: '(' });
      current++;
      continue;
    }

    if (char === ')') {
      tokens.push({ type: 'paren', value: ')' });
      current++;
      continue;
    }

    // 跳过空格
    if (/\s/.test(char)) {
      current++;
      continue;
    }

    // 处理字母（函数名）
    if (/[a-z]/i.test(char)) {
      let value = '';
      while (/[a-z]/i.test(input[current])) {
        value += input[current++];
      }
      tokens.push({ type: 'name', value });
      continue;
    }

    // 处理数字
    if (/[0-9]/.test(char)) {
      let value = '';
      while (/[0-9]/.test(input[current])) {
        value += input[current++];
      }
      tokens.push({ type: 'number', value: Number(value) });
      continue;
    }

    throw new TypeError('未知字符: ' + char);
  }

  return tokens;
}

function parser(tokens) {
  let current = 0;

  function walk() {
    let token = tokens[current];

    // 数字节点
    if (token.type === 'number') {
      current++;
      return {
        type: 'NumberLiteral',
        value: token.value
      };
    }

    // 函数调用
    if (token.type === 'name') {
      let node = {
        type: 'CallExpression',
        name: token.value,
        params: []
      };

      current++; // 跳过函数名
      token = tokens[current];

      if (token.type !== 'paren' || token.value !== '(') {
        throw new Error('应为左括号');
      }
      current++; // 跳过 (
      token = tokens[current];

      // 解析参数
      while (token.type !== 'paren' || token.value !== ')') {
        node.params.push(walk());
        token = tokens[current];
      }

      current++; // 跳过 )
      return node;
    }

    throw new TypeError('未识别的 token: ' + token.type);
  }

  let ast = {
    type: 'Program',
    body: []
  };

  while (current < tokens.length) {
    ast.body.push(walk());
  }

  return ast;
}

function codeGenerator(node) {
  switch (node.type) {
    case 'Program':
      return node.body.map(codeGenerator).join('');

    case 'NumberLiteral':
      return node.value;

    case 'CallExpression':
      const { name, params } = node;

      let operator;
      if (name === 'add') operator = '+';
      else if (name === 'multiply') operator = '*';
      else throw new Error('不支持的函数: ' + name);

      return `(${codeGenerator(params[0])} ${operator} ${codeGenerator(params[1])})`;

    default:
      throw new TypeError('未支持的节点类型: ' + node.type);
  }
}

function compiler(input) {
  const tokens = tokenizer(input);
  const ast = parser(tokens);
  const output = codeGenerator(ast);
  return output;
}

// 使用示例
const input = 'add(2, multiply(3, 4))';
console.log(compiler(input)); // 输出: (2 + (3 * 4))