How to convert day of week name to day of week number

Question

How can I get the integer equivalent of days of the week i.e monday to 2, tuesday to 3, wednesday to 4

Answer 1

Typically, for something like this, you'll likely want to create a function so you don't have to repeat yourself (see DRY). Here's a sample function, that also converts the incoming week day string to lowercase so "Wednesday" will return the same result as "wednesday".

Code (demo)

Note: Comment block with function documentation is using style recommended by JSDoc.

/**
 * @param {String} weekDay
 * @returns {Number} Day of week weekDay is. Returns `undefined` for invalid weekDay.
 */
function getWeekDayNumber(weekDay) {
    var days = {
        sunday: 1,
        monday: 2,
        tuesday: 3,
        wednesday: 4,
        thursday: 5,
        friday: 6,
        saturday: 7
    };

    return days[weekDay.toLowerCase()];
}

var day = getWeekDayNumber("Sunday"); // `day` now equals `1`