Console assert()

Write a message to the console:

console.assert(x + y == 11, "Expression returned false");

Write an object to the console:

const myObj = {firstname:"John", lastname:"Doe"};
console.assert(x + y == 11, myObj);

More examples below.

Description

The assert() method writes a message to the console if an expression evaluates to false.

console.assert( expression, message)

Parameter	Description
expression	Required. Any expression. If the expression evaluates to `false`, a message is written in the console.
message	Required. The message to write in the console.

Check for an element:

console.assert(document.getElementById("demo"), "You have no element with ID 'demo'");

Write an array to the console:

const myArr = ["Orange", "Banana", "Mango", "Kiwi" ];
console.assert(x + y == 11, myArr);

console.assert() is supported in all browsers:


Chrome	Edge	Firefox	Safari	Opera	IE
Yes	Yes	Yes	Yes	Yes	Yes