js实现Scanner

实现基础文本扫描功能

使用字符串的 index 和 substring 方法可以模拟基础扫描功能。以下代码演示如何按空格分割输入字符串：

class TextScanner {
  constructor(text) {
    this.text = text;
    this.position = 0;
    this.delimiter = ' ';
  }

  next() {
    const end = this.text.indexOf(this.delimiter, this.position);
    if (end === -1) {
      const result = this.text.substring(this.position);
      this.position = this.text.length;
      return result;
    }
    const result = this.text.substring(this.position, end);
    this.position = end + 1;
    return result;
  }

  hasNext() {
    return this.position < this.text.length;
  }
}

支持自定义分隔符

扩展扫描器功能使其支持多种分隔符模式：

class EnhancedScanner {
  constructor(text) {
    this.text = text;
    this.position = 0;
    this.delimiters = [' ', '\t', '\n'];
  }

  setDelimiters(delimiters) {
    this.delimiters = delimiters;
  }

  next() {
    let minIndex = this.text.length;
    for (const delim of this.delimiters) {
      const index = this.text.indexOf(delim, this.position);
      if (index !== -1 && index < minIndex) {
        minIndex = index;
      }
    }

    const result = this.text.substring(this.position, minIndex);
    this.position = minIndex === this.text.length ? minIndex : minIndex + 1;
    return result;
  }
}

实现正则表达式匹配

对于更复杂的扫描需求，可以使用正则表达式：

class RegexScanner {
  constructor(text) {
    this.text = text;
    this.position = 0;
    this.pattern = /\s+/;
  }

  setPattern(pattern) {
    this.pattern = new RegExp(pattern);
  }

  next() {
    const remaining = this.text.slice(this.position);
    const match = remaining.match(this.pattern);

    if (!match || match.index !== 0) {
      const result = remaining;
      this.position = this.text.length;
      return result;
    }

    const result = remaining.substring(0, match.index);
    this.position += match.index + match[0].length;
    return result;
  }
}

处理数字和特殊类型

添加特定类型扫描方法：

class TypedScanner extends TextScanner {
  nextInt() {
    const token = this.next();
    return parseInt(token, 10);
  }

  nextFloat() {
    const token = this.next();
    return parseFloat(token);
  }

  nextLine() {
    const oldDelim = this.delimiter;
    this.delimiter = '\n';
    const result = this.next();
    this.delimiter = oldDelim;
    return result;
  }
}

浏览器环境中的输入扫描

在浏览器中处理输入框内容：

function createInputScanner(inputId) {
  const input = document.getElementById(inputId);
  return {
    next: () => {
      const value = input.value.trim();
      input.value = '';
      return value;
    }
  };
}

Node.js 控制台输入处理

使用 Node.js 的 readline 模块实现交互式扫描：

const readline = require('readline');

async function createCLIScanner() {
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
  });

  return {
    next: () => new Promise(resolve => {
      rl.question('', answer => resolve(answer));
    }),
    close: () => rl.close()
  };
}

这些实现提供了不同级别的文本扫描功能，可以根据具体需求选择合适的方案。基础版本适合简单字符串处理，而正则表达式版本则能应对更复杂的文本解析需求。