[Coding Standards] Numeric enums can lead to non-expected behaviour in the runtime

[vpanichkin]

Hey,

first of all, thanks for publishing diia to the Open Source.

While reviewing the code, I saw multiple usages of the numeric enums. In fact, that's quite tricky in typescript.

be-types/src/documents/eResident.ts

Lines 5 to 9 in 174697d

	export enum ResidentshipStatus {
	NotActive = 0,
	Active = 1,
	Terminated = 2,
	}

The code snippet in the runtime will be compiled to the

export var ResidentshipStatus;
(function (ResidentshipStatus) {
    ResidentshipStatus[ResidentshipStatus["NotActive"] = 0] = "NotActive";
    ResidentshipStatus[ResidentshipStatus["Active"] = 1] = "Active";
    ResidentshipStatus[ResidentshipStatus["Terminated"] = 2] = "Terminated";
})(ResidentshipStatus || (ResidentshipStatus = {}));

namely, you will get an object in the runtime with the following structure. I am sure, you didn't want to have "0","1","2" as a possible keys here.

{
    "0": "NotActive",
    "1": "Active",
    "2": "Terminated",
    "NotActive": 0,
    "Active": 1,
    "Terminated": 2
}

Solution:

1. Using enum with the String values:

enum ResidentshipStatus { 
     NotActive = 'notActive', 
     Active = 'active', 
     Terminated = "terminated', 
 } 

will be converted in the runtime to

{
    "NotActive": "notActive",
    "Active": "active",
    "Terminated": "terminated"
}

2. Use object with as const modifier

const ResidentshipStatus = {
    NotActive: 'notActive',
    Active: 'active',
    Terminated: 'terminated',
} as const;

type ResidentshipStatus = typeof ResidentshipStatus[keyof typeof ResidentshipStatus];

In the Javascript runtime, the object will be

"use strict";
const ResidentshipStatus = {
    NotActive: 'notActive',
    Active: 'active',
    Terminated: 'terminated',
};

while the type will stay in the Typescript

More details about this topic can be found using the following links:

• https://www.crocoder.dev/blog/typescript-enums-good-bad-and-ugly/
• https://www.youtube.com/watch?v=jjMbPt_H3RQ

[degloman]

@vpanichkin I belive it is done intentionally, because this field is stored and taken from the database.
Integers reduce database space and improves performance.

[Fire-cell]

@vpanichkin I belive it is done intentionally, because this field is stored and taken from the database. Integers reduce database space and improves performance.

The issue doesn't lie with numbers, root of all is in enum type because it has unpredictable behavior as @vpanichkin described quite well. If numerical values are necessary they can write code like this below:

const ResidentshipStatus = {
NOT_ACTIVE: 0,
ACTIVE: 1,
TERMINATED: 2
} as const