Javascript Вывод даты

Date.prototype.format = function(format = 'yyyy-mm-dd') { 
    if (this.toString() === 'Invalid Date') { 
        return; 
    } 
    const replaces = { 
        yyyy: this.getFullYear(), 
        mm: ('0' + (this.getMonth() + 1)).slice(-2), 
        dd: ('0' + this.getDate()).slice(-2), 
        hh: ('0' + this.getHours()).slice(-2), 
        MM: ('0' + this.getMinutes()).slice(-2), 
        ss: ('0' + this.getSeconds()).slice(-2) 
    }; 
    let result = format; 
    for (const replace in replaces) { 
        result = result.replace(replace, replaces[replace]); 
    } 
    return result; 
}; 
 
console.log(new Date().format()) 
console.log(new Date().format('dd/mm/yyyy hh.MM.ss'))

const date = '2017-10-10 12:10:44'; 
console.log(date.split(' ')[0]);