How can I prepend leading ZEROS on ZIP codes when there are only 3 and 4 digits using LODASH or Typescript?

Question

so, I have the USPS entire CITY, STATE, COUNTY, LAT LON, and ZIP CODE as seen below in the example from said JSON. It's 349,000+ lines long. Very cool.

...

  {
    "zip_code": 988,
    "latitude": 18.393355,
    "longitude": -65.972495,
    "city": "Carolina",
    "state": "PR",
    "county": "Carolina"
  },
  {
    "zip_code": 1001,
    "latitude": 42.140549,
    "longitude": -72.788661,
    "city": "Agawam",
    "state": "MA",
    "county": "Hampden"
  },
...

As you can see, the upper Zip Code has only three digits and the next one, in order has 4 then later down the line there are finally 5 digits.

What I need to do is LOOP through all Zip Codes that === 3 && === 4 and add TWO ZEROS for those Zips with 3 digits and ONE ZERO for Zips with 4 digits.

This NEEDS to be on the fly or need to do a GLOBAL search and replace, ONE TIME, so the add'l Zeros are already there. This comes from the USPS without the leading zeros.

citystatezip is imported like so

import * as citystatezip from 'src/assets/json/city-state-zip-county.json';

Here's what I've tried... or am trying:

  /**
   * @name getAllZips
   * @description gets all the Zips
   * @returns OBJECT Any
   */
  getAllZipCodes(): any {
    let zips = [];
    zips = _.map(citystatezip as unknown as any, 'zip_code');
    let result = _.find(zips, function (n) {
      if (n === 3) {
????????????????
      } else if (n === 4) {
????????????????
      }
    }, 0)
    return result;
  }

UPDATE: Added this as a solution from @Kelly

  getAllZipCodes(): any {
    let zips = [];
    zips = _.map(citystatezip as unknown as any, 'zip_code');
    let result = _.find(zips, function (n) {
         n.toString().padStart(5, "0")
    }, 0)
    return result;
  }

The problem, not with @Kellys solution, is it's not going into the "IF" statement.

Remember, there are 43,625 cities, which is 349000/8 which is the {} and the 6 lines in each. Am I not doing the _.find correctly?

UPDATE 2:

  /**
   * @description set and gets all zip codes
   * @argument nothing
   * @returns zipcodes for get
   */
  public setZipCodes(): void {
    this.zipcodes = this.getAllZipCodes();
  }

  public getZipCodes(): Object {
    return this.zipcodes;
  }

  /**
   * @name getAllZips
   * @description gets all the Zips
   * @returns OBJECT Any
   */
  getAllZipCodes(): any {
    let zips = [];
    zips = _.map(citystatezip as unknown as any, 'zip_code');
    let result = _.find(zips, function (n) {
      return n.toString().padStart(5, "0") <<< like so???
    }, 0)
    this.zipcodes = result;
    return result;
  }

and in the COMPONENT calling the SERVICE above, here's the code in ngOnInit()

    this.allCities = this.elementService.getCities();
    this.allStates = this.elementService.getStates();
    this.allZipcodes = this.vaForm21elementService.getZipCodes();
    console.log("All cities: ", this.allCities);
    console.log("All states: ", this.allStates.default);
    console.log("All zip codes: ", this.allZipcodes);

Answer 1

Replace _.find with map:

let result = zips.map((n) => n.toString().padStart(5, "0"));

padStart pads the start of the string:

988   => 00988
1001  => 01001
31553 => 31553

padStart reference