optional parameters js code example

Example 1: optional function parameter javascript

function check(a, b = 0) {
  document.write("Value of a is: " + a + 
                 " Value of b is: " + b + 
                 "<br>");
}
check(9, 10);
check(1);

Example 2: variable defaults javascript es6

let variableToSet = checkedValue || defaultValue;