isValid() not working properly with format as second parameter

[brunosiqueira]

Description of the Issue and Steps to Reproduce:
isValid() has a weird behavior. Using the browser (momentjs site open), if I type:

moment('2018-dkjsnaksaj x-null').isValid() >> false

But if I set the format of the string as a second parameter, then I get:

moment('2018-dkjsnaksaj x-null', 'YYYY-M-DD').isValid() >> true

Please include the values of all variables used.

Environment:

Chrome 64.0.3282.186
MacOS High Sierra
Both the browser and the OS are important to us, particularly if you have an unsual environment like an IOT application.

Other information that may be helpful:
Thu Mar 01 2018 15:15:41 GMT-0300 (-03)
VM258:2 01/03/2018 15:15:41
VM258:3 180
VM258:4 Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.186 Safari/537.36
VM258:5 2.20.1
undefined

[prendradjaja]

The parser is very forgiving unless strict mode is enabled. See docs here and here for more details.

You probably just want to enable strict mode by passing true as the last argument.

moment('2018-dkjsnaksaj x-null', 'YYYY-M-DD', true).isValid() >> false

@marwahaha

[marwahaha]

Yeah, strict mode will help here. There's more info in this comment.