Simple example of reduce function.

reduce.js

const totalAdresse = docs.reduce((prevValue, contrat) => {
    console.log(prevValue, contrat);
    if (prevValue.includes(contrat.adresse)) {
        return prevValue;
    } else {
        return [...prevValue, contrat.adresse];
    }
}, []);

const totalAchatAndVente = docs.reduce(
    (prevValue, contrat) => {
        if (contrat.achatDevise === hash) {
            return {
                ...prevValue,
                totalAchat: prevValue.totalAchat + contrat.achatAmount,
                contratsAchat: [...prevValue.contratsAchat, contrat],
            };
        }
        if (contrat.venteDevise === hash) {
            return {
                ...prevValue,
                totalVente: prevValue.totalVente + contrat.venteAmount,
                contratsVente: [...prevValue.contratsVente, contrat],
            };
        }

        return prevValue;
    }, {
        totalAchat: 0,
        totalVente: 0,
        contratsAchat: [],
        contratsVente: []
    }
);