HTML DOM
HTML DOM console warn() Method
The console.warn() method outputs a warning message to the browser's developer console. Warnings are highlighted (usually yellow) to draw attention without signalling a hard error.
Definition and Usage
console.warn() logs one or more values to the console as a warning. Browsers typically display it with a yellow background and a warning icon, and often include a stack trace so you can see where the warning was raised.
Syntax
console.warn(message)
console.warn(message, obj1, obj2, ...)It accepts a message string (optionally with format specifiers) followed by any additional values. It returns undefined.
Example
function setAge(age) {
if (age < 0) {
console.warn("Age looks invalid:", age);
age = 0;
}
return age;
}
setAge(-5);
// Console shows a yellow warning: Age looks invalid: -5When a negative age is passed, console.warn flags the suspicious value in yellow but lets the program continue, correcting the value to 0. Warnings are ideal for recoverable or deprecated situations.
Use console.warn for non-fatal issues (like deprecations) and console.error for actual failures, so the console's severity filters remain meaningful.