JSFiddle - React, Tailwind, and code Playground

by mlms13

JavaScript

Date.prototype.getWeek = function() {
    var janFirst = new Date(this.getFullYear(), 0, 1),
        dayOfYear = Math.ceil((this - janFirst) / 86400000),
        firstWeekStart = janFirst.getDay() === 0 ? janFirst.getDay() : 8 - janFirst.getDay(); // Not sure this works

    return Math.ceil((dayOfYear - firstWeekStart) / 7);
};

var d = new Date();
document.writeln(d.getWeek());