In your question you write that moment('03:55jojojo', 'HH:mm',true).isValid();
returns true. This is incorrect. Please check your jsfiddle again.
From http://momentjs.com/docs/
Moment's parser is very forgiving, and this can lead to undesired
behavior. As of version 2.3.0, you may specify a boolean for the last
argument to make Moment use strict parsing. Strict parsing requires
that the format and input match exactly.
moment('It is 2012-05-25', 'YYYY-MM-DD').isValid(); // true
moment('It is 2012-05-25', 'YYYY-MM-DD', true).isValid(); // false
moment('2012-05-25', 'YYYY-MM-DD', true).isValid(); // true
You can use both language and strictness.
moment('2012-10-14', 'YYYY-MM-DD', 'fr', true);
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