Done

class Vacation {
    constructor(organizer, destination, budget) {
        this.organizer = organizer;
        this.destination = destination;
        this.budget = budget;
        this.kids = {};
    }

    registerChild(kidName, kidGrade, kidBudget) {
        if (kidBudget >= this.budget) {

            if (!this.kids.hasOwnProperty(kidGrade)) {
                this.kids[kidGrade] = [];
                this.kids[kidGrade].push({ [kidName]: kidBudget });
                return this.kids[kidGrade].map(element => `${Object.keys(element)}-${Object.values(element)}`);

            } else {
                let checker = false;
                for (let students of this.kids[kidGrade]) {
                    if (Object.keys(students).includes(kidName)) {
                        checker = true;
                    }
                }

                if (checker === false) {
                    this.kids[kidGrade].push({ [kidName]: kidBudget });
                    return this.kids[kidGrade].map(element => `${Object.keys(element)}-${Object.values(element)}`);
                } else {
                    return `${kidName} is already in the list for this ${this.destination} vacation.`;
                }
            }
        } else {
            return `${kidName}'s money is not enough to go on vacation to ${this.destination}.`;
        }
    }

    removeChild(kidName, kidGrade) {
        if (this.kids.hasOwnProperty(kidGrade)) {
            for (let student of this.kids[kidGrade]) {
                if (Object.keys(student).includes(kidName)) {
                    let index = this.kids[kidGrade].indexOf(student)
                    this.kids[kidGrade].splice(index, 1);
                    return this.kids[kidGrade].map(element => `${Object.keys(element)}-${Object.values(element)}`);
                } else {
                    return `We couldn't find ${kidName} in ${kidGrade} grade.`
                }
            }
        } else {
            return `We couldn't find ${kidName} in ${kidGrade} grade.`
        }
    }

    toString() {
        if (this.numberOfChildren === 0) {
            return `No children are enrolled for the trip and the organization of ${this.organizer} falls out...`;
        }

        Object.entries(this.kids).sort((a, b) => a[0] - b[0]);

        let output = `${this.organizer} will take ${this.numberOfChildren} children on trip to ${this.destination}\n`;
        for (const grade in this.kids) {
            output += `Grade: ${grade}\n`;
            let counter = 1;
            for (let test of this.kids[grade]) {
                output += `${counter++}. ${Object.keys(test)}-${Object.values(test)}\n`
            }
        }

        return output;
    }

    get numberOfChildren() {
        let counter = 0;
        for (let kvp in this.kids) {
            for (let kids of this.kids[kvp]) {
                if (kids !== "") {
                    counter++;
                }
            }
        }

        return counter;
    }
}