Typescript - My property decorator isn't working, why? - node.js

Question

I'm trying to construct custom decorators, for example, a decorator to validate the minimum length of a string.
function Min(limit: number) {
return function (target: Object, propertyKey: string) {
let value: string;
const getter = function () {
return value;
};
const setter = function (newVal: string) {
if (newVal.length < limit) {
Object.defineProperty(target, 'errors', {
value: `Your password should be bigger than ${limit}`
});
}
else {
value = newVal;
}
};
Object.defineProperty(target, propertyKey, {
get: getter,
set: setter
});
}
}
In the class, I'm calling this way:
export class User {
#Min(8)
password: string;
}
However, I'm getting this exception:
tslib_1.__decorate([
^
ReferenceError: Min is not defined
at Object.<anonymous>
My tsconfig.json:
{
"compilerOptions": {
"module": "commonjs",
"declaration": true,
"removeComments": true,
"emitDecoratorMetadata": true,
"experimentalDecorators": true,
"importHelpers": true,
"target": "es2017",
"sourceMap": true,
"outDir": "./dist",
"baseUrl": "./",
"incremental": true
},
"exclude": [
"node_modules",
"dist"
]
}
PS: I know there are libraries, for data validations, like the class-validator, however, I would like to create custom decorators for validations and other features.
Where am I going wrong?

Answer 1

It looks like you forgot to import your decorator. Assuming your structure as following:
- decorator.ts
- index.ts
In decorator.ts:
export function Min(limit: number) {
// ...
}
In the index.ts:
// Don't forget to import your decorator here
import { Min } from './decorator';
export class User {
#Min(8)
password: string;
}