JavaScript reference

console.warn

Prints a warning — highlighted in yellow in the console.

Available since: Web API

Syntax

console.warn(...values)

Parameters

Parameter	Type	Description
...values	any	Values to print.

Return value

undefinedReturns nothing.

Examples

A warning about a deprecated option:

function connect(options) {
  if (options.legacy) {
    console.warn('The legacy option is deprecated');
  }
  return 'connected';
}
 
console.log(connect({ legacy: true }));

Output:

The legacy option is deprecated
connected

Notes

Warnings can be filtered in the console separately from regular messages and errors.

In the tutorial

Debugging — How to find bugs in JavaScript: reading the error message, console.log and its variants, checking types, developer tools and debugger.

Thanks for reading!