Convert string to enum in TypeScript

Question

I'm using TypeScript 2.2.1 with target ES5

I have couple of enums like below

enum PermissionLevel {
    ACCOUNT_OWN,
    ACCOUNT_OTHER,
    USER_OWN
}

enum Permission {
    ACCOUNT_CREATE,
    USER_CREATE
}

I have a input JSON as below

{
    "ACCOUNT_OWN": [
        "USER_CREATE",
        "ACCOUNT_CREATE"
    ],
    "ACCOUNT_OTHER": [
        "USER_CREATE"
    ]
}

I want to store this input as Map<Permission, Array<PermissionLevel>>

Following is my code

        // assume authJson is the input and is a valid JSON.
        this.userPermissions = new Map<Permission, Array<PermissionLevel>>();
        for (let [level, permissions] of Object.entries(authJson)) {
            let newLevel: PermissionLevel = <any>PermissionLevel[level];
            for (let perm of permissions) {
                let newPermission: Permission = <any>Permission[perm];
                if (this.userPermissions.get(newPermission)) {
                    this.userPermissions.set(newPermission, this.userPermissions.get(newPermission).concat(newLevel));
                } else {
                    this.userPermissions.set(newPermission, new Array<PermissionLevel>().concat(newLevel));
                }
            }
        }

        console.log(JSON.stringify(this.userPermissions));

The output of the last statement is empty :(. Not sure what I'm doing wrong here.

Update: I just found there are run time errors line below

EXCEPTION: Uncaught (in promise): ReferenceError: PermissionLevel is not defined

Here is a TS fiddle - https://jsfiddle.net/hrwyc6zv/1/

You can access enum value only using the dot notation. The enum is generated as an object in runtime. But the name is not the one from your TS code. It is generated. — amiramw
– amiramw, Commented Jun 6, 2017 at 22:09
I'm using this in an angular 2 application. I just figured I did not export and import PermissionLevel enum correctly. Fixed that. Now when I print the map i.e., console.log(this.userPermissions);, it prints 0's and 1's. I guess they are indexes. Sounds like the map is populated correctly with the Enums... Is that correct ? — TechCrunch
– TechCrunch, Commented Jun 6, 2017 at 22:11

amiramw · Accepted Answer · 2017-06-06 21:56:54Z

1

Map object in javascript is not a JSON. Therefore JSON.stringify doesn't show its actual content.

Small test in Firefox:

var x = new Map()
x.set('a','b')
-> Map { a: "b" }
JSON.stringify(x)
-> "{}"

answered Jun 6, 2017 at 21:56

amiramw

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1 Comment

TechCrunch Over a year ago

What you said is correct. I was debugging it wrong by using stringily on map.

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