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js实现Scanner

2026-02-02 07:38:25JavaScript

实现思路

在JavaScript中实现类似Java的Scanner功能，可以通过监听用户输入或解析字符串来模拟。以下是两种常见场景的实现方法。

方法一：浏览器控制台输入模拟

通过prompt或console交互实现类似Scanner的输入功能，适用于浏览器环境。

class Scanner {
  constructor(input = '') {
    this.input = input.trim();
    this.position = 0;
    this.delimiter = /\s+/; // 默认以空白符分隔
  }

  next() {
    while (this.position < this.input.length && 
           this.input[this.position].match(this.delimiter)) {
      this.position++;
    }
    let start = this.position;
    while (this.position < this.input.length && 
           !this.input[this.position].match(this.delimiter)) {
      this.position++;
    }
    return this.input.slice(start, this.position);
  }

  nextLine() {
    const lineEnd = this.input.indexOf('\n', this.position);
    if (lineEnd === -1) {
      const result = this.input.slice(this.position);
      this.position = this.input.length;
      return result;
    }
    const result = this.input.slice(this.position, lineEnd);
    this.position = lineEnd + 1;
    return result;
  }

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

// 使用示例
const scanner = new Scanner('Hello 123\nWorld');
console.log(scanner.next()); // "Hello"
console.log(scanner.next()); // "123"
console.log(scanner.nextLine()); // "World"

方法二：Node.js 终端输入

在Node.js中通过readline模块实现交互式输入，更接近Java的Scanner体验。

const readline = require('readline');

class Scanner {
  constructor() {
    this.rl = readline.createInterface({
      input: process.stdin,
      output: process.stdout
    });
    this.queue = [];
    this.rl.on('line', (line) => {
      if (this.queue.length > 0) {
        const resolve = this.queue.shift();
        resolve(line);
      }
    });
  }

  async next() {
    return new Promise((resolve) => {
      this.rl.question('', (input) => {
        resolve(input.trim().split(/\s+/).shift());
      });
    });
  }

  async nextLine() {
    return new Promise((resolve) => {
      this.rl.question('', resolve);
    });
  }

  close() {
    this.rl.close();
  }
}

// 使用示例（需在async函数中）
(async () => {
  const scanner = new Scanner();
  console.log('输入内容:');
  const a = await scanner.next();
  const b = await scanner.nextLine();
  console.log(`next: ${a}, nextLine: ${b}`);
  scanner.close();
})();