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JavaScript/Primitive data types/Exercises

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Topic: Primitive Data Types



1. Write a script with the following steps (the 'power'-operator is '**'):

  • Compute the value of 250. Store it in the variable x1.
  • Compute the value of 250 + 1. Store it in the variable x2.
  • Compare x1 with x2. Are they equal?
Click to see solution
"use strict";
const x1 = 2 ** 50;
const x2 = 2 ** 50 + 1;
alert(x1 == x2);         // false



2. Repeat the previous exercise with 260 instead of 250.

Click to see solution
"use strict";
const x1 = 2 ** 60;
const x2 = 2 ** 60 + 1;
alert(x1 == x2);         // true



3. Repeat the previous exercise with 1000 instead of 1.

Click to see solution
"use strict";
const x1 = 2 ** 60;
const x2 = 2 ** 60 + 1000;
alert(x1 == x2);         // false



4. Discuss the results of exercises 1 - 3 with your colleague.



5. Write a script with the following steps:

  • Compute the value of one divided by three. Store the result in the variable x1.
  • Show x1.
  • Multiply x1 by three and store the result in x2.
  • Show x2. Which value do you expect?
Click to see solution
"use strict";
const x1 = 1 / 3;
alert(x1);
const x2 = x1 * 3;
alert(x2);



6. Write a script that shows that 5 and 5.0 are identical values.

Click to see solution
"use strict";
const x1 = 5;
const x2 = 5.0;
alert(x1 == x2);



7. Write a script that

  • asks the user how old he is: prompt(...)
  • prompt() always returns a string. To perform the calculation, it's necessary to convert the answer to number parseInt(), parseFloat(), Number()
  • if his answer is a numeric value, show how often his heart has beaten since his birth (approximately once per second)
  • else, give a message like "Sorry. We need a numeric value to perform the computation."
Click to see solution
// a possible solution:
"use strict";
const answer = prompt("How old are you?");  // returns a string
const age = parseFloat(answer);  // what's about parseInt() or Number() ?
if (Number.isNaN(age)) {         // try other solutions!
  alert("Sorry, we need a number to perform the calculation. You typed: '" + answer + "'");
} else {
  // about one beat per second
  const seconds = age * 365 * 24 * 60 * 60;
  alert("Your heart has beaten (approximately) " + seconds + " times since your birth.");
}



8. Create a HTML page for the previous exercise and embed the solution into the HTML. You can refer to this example.

Click to see solution
<!DOCTYPE html>
<html>
<head>
  <title>Seconds</title>
  <script>
  function go() {
    "use strict";
    let result;
    const answer = document.getElementById("age").value;
    const age = Number(answer);
    if (Number.isNaN(age)) {         // try other solutions!
      result = "Sorry, we need a number to perform the calculation. You typed: '" + answer + "'";
    } else {
      // about one beat per second
      const seconds = age * 365 * 24 * 60 * 60;
      result = "Your heart has beaten (approximately) " + seconds + " times since your birth.";
    }
    document.getElementById("result").innerText = result;
  }
  </script>
</head>
<body>
  <h1>How many times has your heart beaten?</h1>

  <label>Your age: </label>
  <input type="text" id="age">
  <button type="button" onclick="go()">GO</button>
  <p>
    <div id="result">???</div>
  </p>

</body>
</html>



9. What shows the 'alert' statement?

"use strict";
alert(typeof Math.PI);

3.14
float
number
undefined
None of the above