JavaScript Console or Browser console is build-in object in JavaScript which gives access to browser debugging console. console can be used to print output, check errors and warnings in console.

For frontend and web developer, its is recommended to open console window always. We can call global functions, check variables and syntax errors in console.

Open Browser Console

Open console in browser
Browser Console Shortcut for Windows / Linux Console Shortcut for Mac
Chrome Ctrl + Shift + j Cmd + Alt + j.
Firefox Ctrl + Shift + k Cmd + Alt + k
Microsoft Edge Ctrl + Shift + j Cmd + Alt + j.
Internet Explorer Ctrl + 2 or F12 NA
Edge Ctrl + 2 or F12 Cmd + Alt + j
Safari Ctrl + Alt + c Cmd + Alt + c


console.log is used to print output in browser console. We can print string or any others datatype.

console is build-in object and log is method of console.

print in console

Hello JS

    console.log("Hello JS");           

Print variable in console

Tech Altum

    var fname="Tech";         
    var lname="Altum";

Placeholder in console

We can also use Placeholder like %s, %d to insert string or numbers.

String Placeholder

Name is Tech Altum

    var name="Tech Altum";         
    console.log("Name is %s",name);         

Number Placeholder

Id is 12

    var id=12;         
    console.log("Id is %d",id);         

Style console output

To add style in console, use %c and add css property:value in second argument.

This color is red

    console.log("This color is %cred","color:red");    

This text is highlighted

    console.log("This text is %chighlighted text","background:yellow");    

console.log in NodeJS

console.log is also used in NodeJS to print output in terminal.

JS Console


console.warn is used to print warnings in browser console.

⚠️ its a warning

    console.warn('its a warning');


error found

  console.error('error found');


console.table is used to display Arrays and Objects data in console. The argument in table method is either a Array or Object.

Print object in console.table

(index) Value
name avi
id 212


Print array in console.table

(index) Value
0 "abc"
1 "pqr"
2 "xyz"


Print array of object in console.table

(index) name id
0 avi 212
1 isha 200



console.time() is used to measure time ( in ms) taken by task to run.

console.time([label]) starts a new timer. To print code execution time since console.time([label]), use console.timeEnd([label]) method.

timer: 842.64794921875 ms


Check Loop timer

timer: 3310.26611328125 ms

for(var i=1; i<=1000; i++){
    document.querySelector('select.num').innerHTML+="<option>"+ i +"</option>";


console.clear method is used to clear browser console. This will remove all previously printed console messages and print a messages "Console was cleared" in some browsers.

Console was cleared



console.assert method is used to print errors if assertion is false. If it is true, it does nothing.

Assertion failed: console.assert