JavaScript Console - Debug Your Code
In this tutorial, you will learn about the JavaScript console, types of console methods with examples of how to use them.
What is console in javascript?
The console is an object in javascript which is used for debugging and logging results.
Console is a web tool for developers to debug their code. It is used to display information about the code, such as the values of variables, the results of expressions, and the results of function calls. It is also used to display errors and warnings.
Console is a global object so it is available in every scope. It is also available in the global scope of the browser window. You can use it as window.console
or direct console
.
Example:
Example
window.console.log("Hello World!"); // with window
console.log(123); // without window since it is global
console.log(10*5);
console.log(Math.PI);
▶ Try It

Javascript Console Methods
Javascript console
object has multiple methods which give you the ability to log out objects in different ways and to get other related information.
Console in javascript has 8 different methods. Among all console
methods, the log
method is most commonly used.
The 8 console
methods are:
- console.log()
- console.assert()
- console.clear()
- console.count()
- console.dir()
- console.error()
- console.table()
- console.time()
1. console log
console.log()
method is the most commonly used console method. It is used to output a message in the console.
It can output all kinds of objects like string
, number
, boolean
, array
, HTML elements
, etc.
Syntax:
console.log(msg1, msg2, ..., obj1, obj2, ...)
Example:
Example
console.log(123); //number
console.log("Hello World!"); //string
console.log(10 + 20); //expression
console.log(new Date()); //object
▶ Try It
2. console assert
The console.assert()
method asserts (claim) a condition and if the condition is false then output a message in the console. If the assertion is true
then nothing happens.
Syntax:
console.assert(assertion, message, obj1, obj2, ...)
Example:
Example
console.assert(false, "Statement is false");
var num = 10;
console.assert(num > 20, "Number is less than 20");
console.assert(25 === '25', "25 is not equal to '25'", { "SomeObject": 12345 });
▶ Try It

3. console clear
The console.clear()
method clears the console if it is allowed by the environment.
Example
console.log(10);
console.log("Hello World!");
console.clear();
console.log("All above logs cleared");
▶ Try It
4. console count
The console.count()
method logs the number of time count()
method has been called.
The count()
method accepts an argument which is a label to the output, it is logged every time count()
function is called. It is optional, its default value is "default".
Output:

5. console dir
The console.dir()
method displays an interactive list of all the properties of a specified object.
It is presented as a hierarchical listing of methods and properties of an object with closure triangles. Simply console.dir()
let us see all the properties of a specified Javascript object.

6. console error
The console.error()
method outputs an error message to the console.
The error()
method of the console object is used to output the error in the console.
You can output error message or some object on error using console.error()
.
Syntax:
console.error(msg1, msg2, ..., obj1, obj2, ...)
Example:
Example
let num1 = 10, num2 = 0;
if (num2 !== 0) {
console.log(num1 / num2);
}
else {
console.error("divided by 0");
}
▶ Try It
7. console table
console.table()
is used to display data in form of a table.
The method takes 1 mandatory argument data, which must be an array or an object.
Each element in the array becomes a row in the table.
The first column of the table is labeled as an index. For objects index will be property name and for array index are the actual index of array elements.
Example
const arr = ["a", "b", "c", "d", "e"];
console.table(arr);
const user = {
name: "Henry",
id: "iuA98",
age: 22
}
console.table(user);
▶ Try It

8. console time
console.time()
can be used to track how long does an operation takes to execute.
To use console.time()
you have to give a timer a unique name then execute the javascript codes and when you call console.timeEnd()
with the same name then the browser will output the time since timer with the same name started.
Example
console.time("trackLoop");
for (let i = 0; i < 10000; i++) { }
console.timeEnd("trackLoop");
▶ Try It

Conclusion
The console
object is a very useful tool to use in your Javascript code. It can be used to display information, log messages, and track execution time.
You can use console.log()
, console.dir()
, console.error()
, console.table()
, console.time()
and console.timeEnd()
to display information, log messages, error messages, display data in form of a table, track execution time and track execution time.
Frequently asked questions
-
How do I open the JavaScript console?
You can press F12 or you can open the developer tools in your browser. You can also use the shortcut Ctrl + Shift + J or Cmd + Opt + J(in Mac).
-
Why console is used in JavaScript?
The JavaScript console is used for debugging purposes and to display output or some results of your code.