Validate dates on different formats

Question

I have a function that compares different models, one model is from the initial state of the form(the model comes from the backend service, which is a date object), and the other one is when it is converted in the front end.

function getPropertyDifferences(obj1, obj2) { return Object.entries(obj1).reduce((diff, [key, value]) => { // Check if the property exists in obj2. if (obj2.hasOwnProperty(key)) { const val = obj2[key]; // Check if obj1's property's value is different from obj2's. if (val !== value) { return { ...diff, [key]: val, }; } } // Otherwise, just return the previous diff object. return diff; }, {}); } const a = { dateOfBirth: "Wed Jan 06 2021 12:00:05 GMT-0700 (Mexican Pacific Standard Time)", name: "test" }; const b = { dateOfBirth: "2021-01-06T12:00:05.357", name: "test" }; console.log(getPropertyDifferences(a, b));

As you can see, the dates are the same but in different formats; how can I validate in the function that it is the same?

Hint: Try creating and comparing date objects with new Date(stringRepresentation) — Chris Heald
– Chris Heald, Commented Jan 9, 2023 at 16:37
dateOfBirth in b is ambiguous since it doesn't have any timezone information in it, so it depends on the location of the user — Samathingamajig
– Samathingamajig, Commented Jan 9, 2023 at 16:38
at the moment I do not really care about time zone, so I only want to know if 2021-01-06 are equals @Samathingamajig — Jesus
– Jesus, Commented Jan 9, 2023 at 16:52

sai dharmendra kanneganti · Accepted Answer · 2023-01-09 17:27:31Z

Steps taken:

Check if the property is a date using the isNaN() function, which utilizes the valueOf() function of the Date object.
As you said, you only care about the date without the time; we can use toDateString() extension method of the Date object.

function getPropertyDifferences(obj1, obj2) { return Object.entries(obj1).reduce((diff, [key, value]) => { // Check if the property exists in obj2. if (obj2.hasOwnProperty(key)) { const val = obj2[key]; if (typeof val === "string") { const obj1Date = new Date(value); const obj2Date = new Date(val); // check if the values are valid dates. if not, we go through regular comparison if (!isNaN(obj1Date) && !isNaN(obj2Date)) { return obj1Date.toDateString() !== obj2Date.toDateString() ? { ...diff, [key]: val } : diff; } } // Check if obj1's property's value is different from obj2's. if (val !== value) { return { ...diff, [key]: val, }; } } // Otherwise, just return the previous diff object. return diff; }, {}); } const a = { dateOfBirth: "Wed Jan 06 2021 12:00:05 GMT-0700 (Mexican Pacific Standard Time)", name: "test", num: 1 }; const b = { dateOfBirth: "2021-01-06T12:00:05.357", name: "test", num: 2 }; console.log(getPropertyDifferences(a, b));

It is weird that is working here, but when I try to use in code it throw errors in const obj1Date = new Date(value); Argument of type 'unknown' is not assignable to parameter of type 'string | number | Date'., and for isNaN says: Argument of type 'Date' is not assignable to parameter of type 'number'
Oh yeah, I suspect it is because your object might have properties of type numbers, and when you pass a number to the Date constructor, it returns a valid Date object. I also recommend creating a new function that encapsulates the date comparison out of this snippet. I just updated the code snippet, try that and see if it works

Samathingamajig · Accepted Answer · 2023-01-09 16:59:00Z

The ideal option would be new Date(val) !== new Date(value), but since the second time format doesn't include a timezone it is open to interpretation. You also mentioned that you only care about the date itself, not a specific time of day.

function getPropertyDifferences(obj1, obj2) { return Object.entries(obj1).reduce((diff, [key, value]) => { // Check if the property exists in obj2. if (obj2.hasOwnProperty(key)) { const val = obj2[key]; // Check if obj1's property's value is different from obj2's. if (new Date(val.split(" ").slice(2,5).join(" ")) !== new Date(value.split("T")[0])) { return { ...diff, [key]: val, }; } } // Otherwise, just return the previous diff object. return diff; }, {}); } const a = { dateOfBirth: "Wed Jan 06 2021 12:00:05 GMT-0700 (Mexican Pacific Standard Time)", name: "test" }; const b = { dateOfBirth: "2021-01-06T12:00:05.357", name: "test" }; console.log(getPropertyDifferences(a, b));

But it should no return any, because the values should be the same

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