what is double exclamation in javascript code example

Example 1: es6 what is double exclamation operator

!oObject  // inverted boolean
!!oObject // non inverted boolean so true boolean representation

Example 2: javascript double exclamation mark

const isIE8 = !! navigator.userAgent.match(/MSIE 8.0/);  
console.log(isIE8); // returns true or false