How Can I Efficiently Calculate Age from a YYYYMMDD Date String?

Calculate Age Using Date of Birth in YYYYMMDD Format

Calculating an individual's age based on their birth date is a common programming task. Given a birth date in the format YYYYMMDD, numerous approaches can be employed. The question explores an alternative solution to the one that's currently utilized:

var dob = '19800810';
var year = Number(dob.substr(0, 4));
var month = Number(dob.substr(4, 2)) - 1;
var day = Number(dob.substr(6, 2));
var today = new Date();
var age = today.getFullYear() - year;
if (today.getMonth() < month || (today.getMonth() == month && today.getDate() < day)) {
  age--;
}
alert(age);

The proposed solution addresses the issue with the substr method, providing a more concise and optimized approach:

function getAge(dateString) {
    var today = new Date();
    var birthDate = new Date(dateString);
    var age = today.getFullYear() - birthDate.getFullYear();
    var m = today.getMonth() - birthDate.getMonth();
    if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) {
        age--;
    }
    return age;
}

This function simplifies the calculation by directly utilizing the Date object to construct the birth date and extract the necessary information. It also checks for scenarios where the birth month and day haven't yet occurred in the current year, decrementing the age accordingly.

While the original solution is functional, it employs the substr method to extract date components, which can lead to confusion and potential errors. The proposed function offers a more straightforward and efficient method for calculating age based on a provided birth date in the YYYYMMDD format.

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