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dayjs

PropertyValue
Packagedayjs
Versions Covered>=1.10.0 <2.0.0
Contract Version1.1.0
Statusproduction
Last Verified2026-02-27
Maintainercorpus-team

Installation​

npm install dayjs

Covered Functions​

This contract covers 3 function(s):

dayjs()​

Parses date strings and creates Day.js objects (moment.js compatible API)

Import:

import { dayjs } from 'dayjs';

Postconditions​

What happens after calling this function:

🔴 ERROR - dayjs-invalid-date

Condition: input string is not a valid date format

Returns:

Invalid Day.js object (dayjs().isValid() returns false)

Required Handling:

Caller MUST check isValid() before using the Day.js object. Invalid Day.js objects can cause incorrect date calculations, display issues, or NaN values propagating through the application. Use pattern: const d = dayjs(input); if (!d.isValid()) /* handle error */

📖 Source

utc()​

Parses date in UTC mode (requires UTC plugin)

Import:

import { utc } from 'dayjs';

Postconditions​

What happens after calling this function:

🔴 ERROR - utc-invalid-date

Condition: input string is not a valid date format

Returns:

Invalid Day.js object (dayjs().isValid() returns false)

Required Handling:

Caller MUST check isValid() after parsing. Invalid UTC dates can cause timezone calculation errors and data corruption. Use pattern: const d = dayjs.utc(input); if (!d.isValid()) /* handle error */

📖 Source

format()​

Formats dayjs object to string using format tokens

Import:

import { format } from 'dayjs';

Postconditions​

What happens after calling this function:

⚠️ WARNING - format-string-redos

Condition: format string is user-controlled or very long

Returns:

Formatted string (but may cause ReDoS with malicious input)

Required Handling:

Avoid using user-controlled format strings directly. Vulnerable regex patterns in format parsing can cause quadratic time complexity, leading to CPU exhaustion and DoS. Validate and limit format string length. See GitHub PR #2908 for technical details.

📖 Source

Example: Proper Error Handling​

import dayjs from 'dayjs';

async function example() {
  try {
    const result = await dayjs(/* args */);
    // Handle success
    return result;
  } catch (error) {
    // Handle error according to contract postconditions
    console.error('Error:', error);
    throw error;
  }
}

See Also​