Answers for "js specify parameter type in a class method"

javascript multiply arguments

const mul = (...args) => args.reduce((a, b) => a * b);

// Example
mul(1, 2, 3, 4);    // 24

parameters types in javascript

/**
 * My function description
 * @param {String} a
 * @param {String} b
 * @param {Number} amount
 * @example
 * // returns "fooBar fooBar"
 * myFunction('foo', 'Bar', 2)
 * @returns {String}
 */
function myFunction(a, b, amount){
  //do stuff
}
//Note that javascript is not a statically typed language and therefore you
//will not recieve any syntax errors for passing in the wrong types.
//The above code works in Visual Studio Code and intellisense.