Angular ParameterService

parameter.service.ts

import { Injectable } from "@angular/core"
import { ActivatedRoute, ActivatedRouteSnapshot } from "@angular/router"

@Injectable({ providedIn: "root" })
export class ParameterService {

  constructor(private route: ActivatedRoute) { }

  get(property: string, defaultValue: string = null): string {
    const value = this.findProperty(this.route.root.snapshot, property)
    return value || defaultValue
  }

  getNumber(property: string, defaultValue: number = null): number {
    const value = this.findProperty(this.route.root.snapshot, property)
    const numberValue = Number(value)
    const valueIsEmptyOrNull = (value || "").trim() == ""
    const valueIsNaN = numberValue != numberValue
    return valueIsEmptyOrNull || valueIsNan ? defaultValue : numberValue
  }

  private findProperty(
    snapshot: ActivatedRouteSnapshot,
    property: string
  ): string | null {
    const value = snapshot.paramMap.get(property)
    if (value) {
      return value
    }

    for (let i = 0; i < snapshot.children.length; ++i) {
      const child = snapshot.children[i]
      const childValue = this.findProperty(child, property)
      if (childValue) {
        return childValue
      }
    }
                                                 
    return null
  }
}