Unwritten type=button on the button causes it to be submitted when clicked

There is a place very strange: click a popover button, did not think of popover disappeared, after the company's js master debugging, found the mystery

 
<button class="btn btn_set_wj" onclick="add_q()"> Add questionnaire </button> 

Just add a type ="button" :

 
<button class="btn btn_set_wj" type ="button" onclick="add_q()"> Add questionnaire </button> 

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