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

You could also use the "indexOf" function of javascript.

var days  = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];

console.log(days.indexOf('Sunday')); // return 0
console.log(days.indexOf('Tuesday')); // return 2

But remember that "indexOf" is case sensitive and that it will return "-1", if the string is not in the array.

Answer 2

Can use a lookup object:

var days = {
    sunday: 1,
    monday: 2,
    tuesday: 3,
    wednesday: 4,
    thursday: 5,
    friday: 6,
    saturday: 7
}

console.log(days["sunday"]) //1

Now, simply access any of the above properties and it's value will be the numeric day of the week!

console.log(days["monday"]) //2

Answer 3

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`