JavaScript/Functions/Exercises

Topic: Functions

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1. Define a function with one parameter. The function returns a string starting with "The given argument was: " and ends with ". Ok?". Insert the argument between those two strings.

Click to see solution

"use strict";

// declare the function
function decorate(str) {
  const ret = "The given argument is: " + str + ". Ok?";
  return ret;
}

// call the function
let tmp = decorate("Francis");
alert(tmp);

tmp = decorate("Drake");
alert(tmp);

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2. Extend the previous function to handle different data types, e.g., Numbers, Objects, ... . Show the data type into the returned string.

Click to see solution

"use strict";

// declare the function
function decorate(param) {

  let dataType = "";
  let paramAsString = "";

  switch (typeof param) {
    case "object":
      dataType = "object";
      paramAsString = JSON.stringify(param);
      break;
    case "string":
      dataType = "string";
      paramAsString = param;
      break;
    // next case ...
    default:
      dataType = "???";
      paramAsString = param;
  }
  const ret = "The given argument is: " + paramAsString + " It's data type is: " + dataType + ". Ok?";
  return ret;
}

// call the function
let tmp = decorate("Francis");
alert(tmp);

tmp = decorate(42);  // a number
alert(tmp);

tmp = decorate({temperature: "25° C"}); // an object
alert(tmp);

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3. Define a function that takes two parameters. The function returns the average of both.

Click to see solution

"use strict";

// declare the function
function average(num1, num2) {
  return (num1 + num2) / 2;
}

// call the function
alert(average(2, 4));

alert(average(2.4, 2.6));

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4. Define the function of the first exercise with an arrow function.

Click to see solution

"use strict";

// declare the function and reverence it by a variable
const decorate = (str) => "The given argument is: " + str + ". Ok?";

// call the function
let tmp = decorate("Francis");
alert(tmp);


// or, even more compact:
tmp = (str => "The given argument is: " + str + ". Ok?")("Drake");
alert(tmp);

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5. Define a function that takes an array of numbers as its parameter. The function returns the array's length, the smallest element, the largest element, and the average of all elements.

Because a function can return only a single element, all those computed values must be packed into an array (or an object). This array is the return value.

Click to see solution

"use strict";

function checkArray(arr) {

  // local variables
  let min = arr[0];
  let max = arr[0];
  let sum = 0;

  // a 'forEach' construct with an anonymous function
  arr.forEach((elem) => {
    if (elem < min) { min = elem };
    if (elem > max) { max = elem };
    sum = sum + elem;
  });

  // the length and average can be computed here
  // 'pack' everything in an array:  []
  return [arr.length, min, max, sum / arr.length];
}

// the return value is an array
let ret = checkArray([2, 4, 6, 8]);
alert(ret);

// or:
let [length, min, max, avg] = checkArray([2, 4, 6, 8, 10]);
alert ("Length: " + length + ", Min: " + min + ", Max: " + max + ", Average: " + avg);

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6. Define a function for describing a car. It takes four parameters: producer, model, horsepower, and color. The first two are mandatory; the last two are optional. Define default values for the last two parameters, e.g., "unknown".

Click to see solution

"use strict";

// supply default values if they are not given
function showCar(producer, model, horsepower = "unknown", color = "unknown") {

  let ret = "";
  if (!producer || !model) {
    return "Producer and model must be specified";
  }
  ret  = "My car is produced by " + producer;
  ret +=  ". The model is: " + model;
  ret +=  ". The horsepower is: " + horsepower;
  ret +=  ". The color is: " + color;

  return ret;
}

alert(showCar("Ford", "Mustang", 300, "blue"));
alert(showCar("Ford", "Mustang GT", 350));

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1 What is the result?

"use strict";

alert(func("Hello"));

function func(param) {
  return param + " world";
} //

	Hello world
	Runtime error
	None of the above

2 What is the result?

"use strict";

function func(param) {
  param = "ppp";
  return param;
} //

let x = "xxx";

alert(x);
alert(func(x));
alert(x);

	xxx, xxx, xxx
	xxx, ppp, ppp
	xxx, ppp, xxx
	None of the above