JavaScript Tutorial

The language for programming web pages.

Chapter Quiz Exercises

JS Data Types

JavaScript Data Types

JavaScript has 8 data types. The typeof operator returns the type of a variable.

Primitive Types:

String — text: "Hello"
Number — numeric: 42, 3.14
BigInt — large integers: 9007199254740991n
Boolean — true / false
Undefined — declared but no value
Null — intentionally empty
Symbol — unique identifier

Reference Type:

Object — arrays, objects, functions

Try It Yourself

Edit the code below and click Run to see the result live.

Source Code

<!DOCTYPE html>
<html>
<body style="font-family:Arial; padding:20px;">
  <h2>typeof Operator</h2>
  <div id="out" style="background:#1e1e1e; color:#abb2bf; padding:15px; border-radius:8px; font-family:monospace; line-height:2.2; min-height:100px;"></div>
  <button onclick="showTypes()" style="margin-top:10px; padding:10px 20px; background:#f7df1e; color:#1a1a2e; border:none; border-radius:5px; cursor:pointer; font-weight:bold;">▶ Show Types</button>
  <script>
    function showTypes() {
      const data = [
        ["Hello World", typeof "Hello World"],
        [42, typeof 42],
        [3.14, typeof 3.14],
        [true, typeof true],
        [undefined, typeof undefined],
        [null, typeof null],
        [{name:"Ali"}, typeof {name:"Ali"}],
        [[1,2,3], typeof [1,2,3]],
        [function(){}, typeof function(){}],
        [Symbol(), typeof Symbol()],
      ];
      let html = "";
      data.forEach(d => {
        html += `<span style="color:#e5c07b">typeof</span> <span style="color:#98c379">${JSON.stringify(d[0])}</span> = <span style="color:#c678dd">"${d[1]}"</span><br>`;
      });
      document.getElementById("out").innerHTML = html;
    }
  </script>
</body>
</html>

Result

Topics

JS Introduction JS Where To JS Output JS Variables JS Data Types JS Functions JS Objects JS Arrays JS Strings JS If Conditions JS Loops JS Math JS Errors JS Scope JS DOM JS Events JS Promises & Async JS Classes JS JSON JS RegExp