js is function code example

Example 1: check if function javascript

variableToCheck instanceof Function

Example 2: How to create a function in javascript

function addfunc(a, b) {
  return a + b;
  // standard long function
}

addfunc = (a, b) => { return a + b; }
// cleaner faster way creating functions!

Example 3: isfunction javascript

function isFunction(functionToCheck) {
 return functionToCheck && {}.toString.call(functionToCheck) === '[object Function]';
}