electron/lib/renderer/remote/callbacks-registry.ts

const v8Util = process.electronBinding('v8_util')

export class CallbacksRegistry {
  private nextId: number = 0
  private callbacks = new Map<number, Function>()

  add (callback: Function) {
    // The callback is already added.
    let id = v8Util.getHiddenValue<number>(callback, 'callbackId')
    if (id != null) return id

    id = this.nextId += 1

    // Capture the location of the function and put it in the ID string,
    // so that release errors can be tracked down easily.
    const regexp = /at (.*)/gi
    const stackString = (new Error()).stack
    if (!stackString) return

    let filenameAndLine
    let match

    while ((match = regexp.exec(stackString)) !== null) {
      const location = match[1]
      if (location.includes('(native)')) continue
      if (location.includes('(<anonymous>)')) continue
      if (location.includes('electron/js2c')) continue

      const ref = /([^/^)]*)\)?$/gi.exec(location)
      if (ref) filenameAndLine = ref![1]
      break
    }

    this.callbacks.set(id, callback)
    v8Util.setHiddenValue(callback, 'callbackId', id)
    v8Util.setHiddenValue(callback, 'location', filenameAndLine)
    return id
  }

  get (id: number) {
    return this.callbacks.get(id) || function () {}
  }

  apply (id: number, ...args: any[]) {
    return this.get(id).apply(global, ...args)
  }

  remove (id: number) {
    const callback = this.callbacks.get(id)
    if (callback) {
      v8Util.deleteHiddenValue(callback, 'callbackId')
      this.callbacks.delete(id)
    }
  }
}