trees.js

const getTree = barcode => {
    const barcodeLength = barcode.length;
    const firstTwoDigits = parseInt(barcode.slice(0,2));
    
    const dic = {
        'bluecypress': {digits: [45,56], length: 8, name: 'Blue Ice Arizona Cypress'},
        'palm': {digits: [76, 43], length: 12, name: 'The Palm Tree'},
        'maple': {digits: [23, 12,45,54], length: 6, name: 'Maple Trees'}
    };
    
    const [_, {name}] =  Object.entries(dic).find(([key, {digits, length}])=>
        digits.includes(firstTwoDigits) && length===barcodeLength
    );

    return name;
};

getTree('545456'); //Maple Trees


//Initial Approach
// const getTree = (barcode) => {

//     const dic = {'bluecypress': {digits: [45,56], length: 8}, 'palm': {digits: [76, 43], length: 12}, 'error': 'Not Found'};
//     const names = {'bluecypress': 'Blue Ice Arizona Cypress', 'palm': 'The Palm Tree'};

//     const code =  [...Object.keys(dic)].find(key=> {
//         const [first, second] = dic[key].digits;
//         const digits = barcode.slice(0,2);
//         return digits===`${first}` || digits === `${second}`;
//     });
//     if(dic[code].length === barcode.length) {
//         return names[code];
//     } else {
//         return dic['error']
//     }
// }


// getTree('76435235345'); //It should return 'The Palm Tree'

My own implementation of the Luhn Algorithm (based on https://en.wikipedia.org/wiki/Luhn_algorithm):

const checkLuhn = cardNumber => {
    const sum = [...cardNumber].reduceRight((prev, curr, i, arr) =>
        prev+= (i%2)?Number(arr[Number(curr)]):Number(curr)
    ,0);
    return sum && sum % 10 === 0;
}