Several observers of Donald Trump have commented that the Republican nominee rarely seems to genuinely laugh.

Many would say that Donald Trump is an expressive person, but some are wondering if he ever really laughs.
A CNN piece on the topic states that “he certainly jokes. He grins, winks, puckers and preens."
However, observers who closely followed the candidate have reportedly had difficulty finding examples of him laughing for real.
There seems to be one commonly referenced video posted online which shows Trump exhibiting genuine laughter; it occurred during a campaign speech when he heard a barking sound and someone from the audience suggested it was Hillary Clinton. 
And though Trump has demonstrated a sense of humor, it often seems to have an underlying meanness.  
When he ran for the GOP nomination, the candidate hosted 'Saturday Night Live,' but he also frequently called his opponents names like "Lyin' Ted Cruz" to make audiences laugh.  
As Gawker points out, his sense of fun likely reflects his own self-perception, “Nobody takes Trump more seriously than Trump, and there’s no question that he is utterly lacking in a sense of humor about himself.”