Util function to proxy a function arguments and do something with them (not harming the default function implementation)

hookInto.js

/**
 * hookInto
 *
 * This will hook into a function of an object so we can check the arguments
 * used when it is called any time and do some calculations on those arguments.
 *
 * @param {object} targetObject Object where the function you want to target is
 * @param {string} functionName The name of the function you want to target
 * @param {function} handler The hook function that will handle the arguments
 * @returns {undefined}
 */
function hookInto(targetObject, functionName, handler = () = >{}) {
  // save the original function
  const backupFunction = targetObject[functionName]
  // overwrite the original function and set the handler
  targetObject[functionName] = function(...args) {
    // handle the arguments with the custom handler
    handler(...args)
    // trigger the original function as normal
    backupFunction.apply(targetObject, args)
  }
}

// Example:
// hookInto(localStorage, 'setItem', (...args) => { console.log(args) })