Classes versus co-data

ClassWhoAmI.js

class ClassWhoAmI {
    #prefix = 'It is the secret'
    suffix = 'person'
    static additional = 'bad one'

    constructor(parameter) {
        this.parameter = parameter
    }

    getValue() {
        return `${this.#prefix}: ${this.parameter} ${this.suffix}`
    }
}

var testClassObject = new ClassWhoAmI("I'm")
testClassObject.suffix = 'programmer'
console.log(testClassObject.getValue(), '-', ClassWhoAmI.additional)

DataWhoAmI.js

var DataWhoAmI = Object.assign((parameter) => {
    var prefix = 'It is the secret'
    var coData = {
        suffix: 'person',
        getValue: () => `${prefix}: ${parameter} ${coData.suffix}`
    }
    return coData
}, {additional: 'good one'})

var testDataObject = DataWhoAmI("I'm")
testDataObject.suffix = 'programmer'
console.log(testDataObject.getValue(), '-', DataWhoAmI.additional)

FuncWhoAmI.js

function FuncWhoAmI(parameter) {
    this.suffix = 'person'
    this.parameter = parameter
}
FuncWhoAmI.additional = 'old one'
FuncWhoAmI.prototype.getValue = function () {
    return `It can not be a secret: ${this.parameter} ${this.suffix}`
}

var testFuncObject = new FuncWhoAmI("I'm")
testFuncObject.suffix = 'programmer'
console.log(testFuncObject.getValue(), '-', FuncWhoAmI.additional)