Youtube 頻道：https://www.youtube.com/c/kaochenlong

如果畫面太小或看不清楚
可移駕至 https://www.youtube.com/watch?v=N2nmdRQWPlw 觀看 4K 高畫質版本

GitHub 專案：https://github.com/kaochenlong/cann-lang

程式碼：

檔名：src/helpers.ts

const isNumber = (char: string): boolean => /\d/.test(char)

export { isNumber }

檔名：tests/tokenizer.test.js

import { describe, it } from "https://deno.land/std@0.156.0/testing/bdd.ts"
import { expect } from "https://deno.land/x/expect@v0.2.10/mod.ts"
import { Tokenizer } from "../src/tokenizer.ts"

describe("Tokenizer", () => {
  it("處理數字", () => {
    const input = `9527`
    const result = {
      type: "NUMBER",
      value: 9527,
    }

    const t = new Tokenizer(input)
    expect(t.nextToken()).toEqual(result)
  })
})

檔名：src/tokenizer.ts

import { isNumber } from "./helpers.ts"

type Token = {
  type: string
  value: any
}

class Tokenizer {
  private input: string
  private cursor: number

  constructor(input: string) {
    this.input = input
    this.cursor = 0
  }

  nextToken(): Token | null {
    if (this.input.length === this.cursor) {
      return null
    }

    const str = this.input.slice(this.cursor)

    // 如果是數字的話...
    if (isNumber(str[0])) {
      let result = ""

      while (isNumber(str[this.cursor])) {
        result += str[this.cursor]
        this.cursor++
      }

      return {
        type: "NUMBER",
        value: +result,
      }
    }

    return null
  }
}

export { Tokenizer }

如果喜歡這個系列的影片，歡迎訂閱我的頻道
或是想聽我介紹一些別的內容，也可直接在這裡或 YouTube 頁面下方留言 :)