What is the Console API?

The Console API helps you inspect JavaScript while you are building a page. It writes information to the browser's developer tools instead of changing the page for visitors.

Open the Console

Open the browser's developer tools with the menu or with Ctrl+Shift+I, then choose the Console tab. You can also right-click a page and choose Inspect. The exact menu label may differ between browsers.

Try console.log()

const userName = 'Yugien';
console.log('userName:', userName);

Run this code in the Console. The label makes the output easier to scan when several values are logged.

Read errors carefully

notDefinedFunction();

The Console reports that the function is not defined and points to a source location. Read the first useful error and its location before changing unrelated code.

Common mistakes

• Do not use Console output as the only feedback for visitors.
• Remove logs that expose private data before publishing.
• Use breakpoints and the debugger when repeated logging is not enough.