How to replace code before transpiling TypeScript code using Rollup. (How to transpile TypeScript code with Private Class Fields to ES5.)

I wont to do

I want to transpile TypeScript code with Private Class Fields to ES5 like when using TypeScript’s private identifier.

(I give up one or the other, it will be resolved soon. But I don’t want to give up.)

I did

I tried to replace code before transpiling TypeScript code using Rollup.

// ./src/index.mts
export class Foo {
  #foo = 0
  #bar = 'a'
  get foo() {
    return this.#foo
  }
  set foo(value) {
    this.#foo = value
  }
  get bar() {
    return this.#bar
  }
  set bar(value) {
    this.#bar = value
  }
}

// rollup.config.mjs
import replace from '@rollup/plugin-replace'
import typescript from '@rollup/plugin-typescript'
export default {
  input: './src/index.mts',
  output: {
    file: './dist/index.js',
    format: 'iife'
  },
  plugins: [
    replace({ // Assumption that ' #' and '.#' are not used in strings, regular expressions, etc.
      ' #': ' private _',
      '.#': '._',
      delimiters: ['', '']
    }),
    typescript({compilerOptions: {target: 'es5'}})
  ]
}

result

JavaScript code using WeakMap is output. Not appear to be replaced.

Changing from ' private _' to ' _', same result.

How can I solve what I want?

note

In JavaScript file, expected result is output.

So I see nothing wrong with Rollup replace plugin part.

// rollup.config.mjs
import replace from '@rollup/plugin-replace'
export default {
  input: './src/index.mjs',
  output: {
    file: './dist/index.js',
    format: 'iife'
  },
  plugins: [
    replace({ // Assumption that ' #' and '.#' are not used in strings, regular expressions, etc.
      ' #': ' _',
      '.#': '._',
      delimiters: ['', '']
    })
  ]
}

// ./src/index.mjs (same as ./src/index.mts)
export class Foo {
  #foo = 0
  #bar = 'a'
  get foo() {
    return this.#foo
  }
  set foo(value) {
    this.#foo = value
  }
  get bar() {
    return this.#bar
  }
  set bar(value) {
    this.#bar = value
  }
}