Unhandled edge case for isValid() function.

[Niluk98]

Describe the bug
I was using moment in my project. I wanted to use a if-condition that will execute a peice of code based on a condition that If the date string that I am getting is a valid date string then only it will proceed else it won't. But somehow the date string was coming undefined. Surprisingly, moment(undefined).isValid() was returning true. It should return false

To Reproduce
Steps to reproduce the behavior:
Just code this line : console.log(moment(undefined).isValid()); //output TRUE

Expected behavior
Output should be false.

Desktop (please complete the following information):

• OS: ubuntu
• Browser firefox

Moment-specific environment

• The time zone setting of the machine the code is running on
• The time and date at which the code was run
• Other libraries in use (TypeScript, Immutable.js, etc)

Please run the following code in your environment and include the output:

console.log((new Date()).toString())
console.log((new Date()).toLocaleString())
console.log((new Date()).getTimezoneOffset())
console.log(navigator.userAgent)
console.log(moment.version)

Additional context
Add any other context about the problem here.

[antarilos]

The point is that moment(undefined) is the same as moment(), so in both statements a Moment object with the current time and date is returned.

I would suggest, assuming your date string is stored in myStringDate variable, to use:

if (myStringDate && moment(myStringDate).isValid()) {
  // Do whatever is needed when the date is valid
}

Just in case you would prefer an early return pattern:

if (!myStringDate || !moment(myStringDate).isValid()) {
  return;
}
// Do whatever is needed when the date is valid