Logging

JavaScript logging is similar to logging in basically every other language.

Basic Log Levels

JavaScript offers several built-in logging methods, each with a specific purpose. The most commonly used are:

Used for general output of information to the console. It's often used for basic debugging or status messages.

console.log('Just general output');

Used to display informational messages that are not errors but important to note.

console.info('Some basic information');

Used to indicate potential problems or warnings that don't stop the execution of the program but might lead to issues.

console.warn('Hey this could be important');

Used to log error messages when something goes wrong, especially when an exception occurs.

console.error('SOMETHING HAS GONE WRONG');

Used for detailed debugging information. In some browsers, these messages may be hidden by default unless you enable verbose logging.

console.debug('Psst, I am a sneaky message');

It is also possible to pass entire objects or arrays of objects to the logging functions. These then get logged out nicely in JSON.

const user = {
  name: 'Alice',
  age: 30,
  occupation: 'Engineer'
};

console.log('User object:', user);

This will result in something like this (may look different depending on your browser):

User object: Object { name: "Alice", age: 30, occupation: "Engineer" }

Of course the same also works for arrays of objects.

const users = [
  { name: 'Alice', age: 30 },
  { name: 'Bob', age: 25 },
  { name: 'Charlie', age: 35 }
];

console.log('Array of users:', users);

Which then results in:

Array of users: Array(3) [ 0: Object { name: "Alice", age: 30 }, 1: Object { name: "Bob", age: 25 }, 2: Object { name: "Charlie", age: 35 } ]

Fun fact: you can also display an array as a table with the console.table() function!