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Validating string date format in JavaScript involves verifying if a given string conforms to a specific date format, such as YYYY-MM-DD or MM/DD/YYYY. This ensures the string represents a valid date before further processing or manipulation.
There are many ways by which we can validate whether the Date format is correct or not, Let’s discuss each of them one by one.
We will explore all the above methods along with their basic implementation with the help of examples.
Approach 1: Using the Date.parse() Inbuild FunctionIn this approach, we are using Date.parse() which takes a string as an argument to calculate the milliseconds since “1-jan-1970” and returns the result in milliseconds. NaN will check for the number validation if it returns false means it is not a valid date else it is a valid date.
Syntax:
Date.parse( datestring ); Example: It describes the validation of date format using the Date.parse() inbuild function.
JavaScript
// Creating variables
let Date1 = "2023-08-25";
let Date2 = "Invalid date string format";
// Function for validation of date format
function isValidDate(stringDate) {
return !isNaN(Date.parse(stringDate));
}
// Displaying the result
console.log(isValidDate(Date1));
console.log(isValidDate(Date2));
Approach 2: Using Regular Expression For date format validation, we are using regular expressions. This entails creating a pattern to match particular text formats, which can be customized according to the required date format.
Type of formats:
- “YYYY-MM-DD”
- “DD-MM-YYYY”
- “DD/MM/YYYY”
Syntax:
// Format 1: "YYYY-MM-DD"
const regex = /^\d{4}-\d{2}-\d{2}$/;
// Format2 : "DD-MM-YYYY"
const regex = /^(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])-(\d{4})$/;
// Format3 : "DD/MM/YYYY"
const regex = /^(0[1-9]|1[0-2])\/(0[1-9]|1[0-2])\/\d{4}$/;
Example: It describes the string date validation using regular expressions in different ways.
JavaScript
let Date1 = "06-24-2013";
let Date2 = "2013-18-09";
// Format 1: "YYYY-MM-DD" (Y-year, M- month, D - date)
function isValidDate(stringDate) {
const regex = /^\d{4}-\d{2}-\d{2}$/;
return regex.test(stringDate);
}
console.log(isValidDate(Date1)); // Output: false
console.log(isValidDate(Date2)); // Output: true
// Format2 : "DD-MM-YYYY" (Y-year , M- month , D - date)
let Date3 = "2013-18-09";
let Date4 = "06-24-2013";
function isValidDate1(stringDate) {
const regex = /^(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])-(\d{4})$/;
return regex.test(stringDate);
}
console.log(isValidDate1(Date3)); // Output: false
console.log(isValidDate1(Date4)); // Output: true
// Format3 : "DD/MM/YYYY" (Y-year , M- month , D - date)
let Date5 = "2013-18-09";
let Date6 = "06-24-2013";
let Date7 = "06/12/2013";
let Date8 = "06/4/2013";
function isValidDate2(stringDate) {
const regex = /^(0[1-9]|1[0-2])\/(0[1-9]|1[0-2])\/\d{4}$/;
return regex.test(stringDate);
}
console.log(isValidDate2(Date5)); // Output: false
// Month can't be more than 12
console.log(isValidDate2(Date6)); // Output: false
console.log(isValidDate2(Date7)); // Output: true
// Month should have 2 digits
console.log(isValidDate2(Date8)); // Output: false
Outputfalse
true
false
true
false
false
true
false
In this approach, we are using instanceof operator which makes an instance of a date and if it is a valid date object then it will return true else it will return false. The !isNan() function can be used to determine whether the date in the Date object is valid.
Syntax:
let gfg = objectName instanceof objectType
Example: It describes the string date validation using instance of the operator.
JavaScript
// Creating variable having different values
let str = "13/2019/jan";
let str1 = "2019/jan/13";
let str2 = "jan/13/2019";
let str3 = "13/13/2019";
// Function for validation of date
function isValidDate(str) {
let date = new Date(str);
let ans = (date instanceof Date) && !isNaN(date);
return ans;
}
// Printing out the result in console
console.log(isValidDate(str)); //true
console.log(isValidDate(str1)); //true
console.log(isValidDate(str2)); //true
//false : invalid daate format
console.log(isValidDate(str3));
Outputtrue
true
true
false
Regardless of the date format, the JavaScript code Object.prototype.toString.call(date) === ‘[object Date]’ is frequently used to verify whether an object is an instance of the Date class. It return the date object if it is a valid date object and it is not NaN then it will true else it will return false.
Syntax:
obj.toString()
Example: It describes the string date validation using Object.prototype.toString.call() function.
JavaScript
// Function for validation of date format
function isValiDate(str) {
let date = new Date(str);
let ans =
Object.prototype.toString.call(date) === "[object Date]"
&& !isNaN(date);
return ans;
}
// DD-MM-YYYY
let str = "13-jan-2019";
// MM-DD-YY
let str1 = "jan-19-13";
// DD-YY-MM
let str2 = "13-19-jan";
// DD/YY/MM
let str3 = "13/19/jan";
// DD/YY/MM (month in number)
let str4 = "13/19/01";
console.log(isValiDate(str));
console.log(isValiDate(str1));
console.log(isValiDate(str2));
console.log(isValiDate(str3));
console.log(isValiDate(str4));
Outputtrue
true
true
true
false
Approach 5: Using Moment.js LibraryMoment.js is a javascript library which is used to validate the Date. It has a function “moment” which can two aruments and it returns true if the date argument matches to the formate arument else it will return false.
Syntax : moment(date , format).isValid();
OR
moment(date: String).isValid()
Example: This describes how to validate string date format using moment library in JavaScript.
JavaScript
// Importing moment into js file
const moment = require('moment');
// Function for validation of date format
function isValidDate(dateString, format) {
return moment(dateString, format, true).isValid();
}
let Date1 = "2023-04-15";
let Date2 = "15-04-2023";
// Displaying the output
// Output: true
console.log(isValidDate(Date1, "YYYY-MM-DD"));
// Output: false
console.log(isValidDate(Date2, "YYYY-MM-DD"));
Output
true
false
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