Comparing Dates with JavaScript: Beyond Equality

When dealing with dates in JavaScript, comparing them for greater than, less than, and non-past values is crucial for various applications. Text box inputs provide a convenient way to gather dates, but we need to explore how to compare them effectively.

The Date object in JavaScript offers a straightforward solution. Create an instance for each date to effortlessly compare them using comparison operators like , =. However, it's worth noting that equality comparisons (== and !=) require a different approach.

To compare equality, use date.getTime(). As demonstrated in the example below:

var d1 = new Date();
var d2 = new Date(d1);
var same = d1.getTime() === d2.getTime();
var notSame = d1.getTime() !== d2.getTime();

Direct equality checks with the Date objects using == or === will yield incorrect results, as the below snippet illustrates:

console.log(d1 == d2);   // false
console.log(d1 === d2);  // false
console.log(d1 != d2);   // true
console.log(d1 !== d2);  // true
console.log(d1.getTime() === d2.getTime()); // true

In summary, use date.getTime() for precise equality comparisons. It's also recommended to employ constrained forms of date entry, such as drop-downs, to avoid potential input validation issues.