Generally Joker, is considered as extremely beneficial or an extremely harmful character. For example in Cards, it is considered as the highest trump card and in Poker, it is wild. That's exactly how the character is shown in the film as well.
In psychology, personality type refers to the psychological classification of different types of individuals. Personality types are sometimes distinguished from personality traits, with the latter embodying a smaller grouping of behavioral tendencies.
In which, The Myers-Briggs Personality Type Indicator is a self-report inventory designed to identify a person's personality type, strengths, and preferences. The questionnaire was developed by Isabel Myers and her mother Katherine Briggs based on their work with Carl Jung's theory of personality types. In total there are a total of 16 Different MBTI Personality Types:
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So what exactly is Joker's Personality?
Further, every Personality type has a certain number of personality traits , Personality trait a relatively stable, consistent, and enduring internal characteristic that is inferred from a pattern of behaviors, attitudes, feelings, and habits in the individual.
Traits are important and interesting because they describe stable patterns of behaviour that persist for long periods of time (Caspi, Roberts, & Shiner, 2005). Importantly, these stable patterns can have broad-ranging consequences for many areas of our life (Roberts, Kuncel, Shiner, Caspi, & Goldberg, 2007).
Joker being an ENTP, he is dominant with Extraverted Intuiting (Ne), which is one of 8 Cognitive functions to taking in information, these are called perceiving functions, Extraverted intuiting is one of them.
People with dominant Ne tend to be very articulate speakers who can speak quickly, fluidly and with ease. When speaking ideas come easily to them and they rapidly turn those into words, whole sentences and complete stories and that's how people are attracted one of the all time most favourite character;