console API

The WHATWG Console standard for logging and debugging.

Global

Global	Type	Description
console	object	Logging and debugging interface

Methods

console.log(...args)

Log informational messages. Arguments are space-separated in output.

console.log('Hello, world!');
console.log('Value:', 42, 'Status:', true);
console.log({ key: 'value' });  // objects serialized

console.info(...args)

Alias for console.log.

console.info('Server started on port 8080');

console.warn(...args)

Log a warning message. Prefixed with [WARN] in output.

console.warn('Deprecated API called');
console.warn('Memory usage:', process.memoryUsage());

console.error(...args)

Log an error message. Prefixed with [ERROR] in output.

console.error('Failed to connect to database');
console.error('Error details:', err.message, err.stack);

console.debug(...args)

Log a debug message. Prefixed with [DEBUG] in output.

console.debug('Request headers:', JSON.stringify(headers));

Log Levels

Each method maps to a numeric log level included in the output prefix:

Method	Level	Value
console.debug()	DEBUG	0
console.log() / .info()	INFO	1
console.warn()	WARN	2
console.error()	ERROR	3

Implementation

console.* runs on qzjs's internal thread and writes to the host process's standard error, formatted as [qzjs:<level>] <message>. There is no host callback for console — output goes straight to stderr.

Formatting

Arguments are converted to strings via String(). Objects serialized with JSON.stringify may truncate circular references. Complex objects are best logged one property at a time.

Notes

• No console.table(), console.group(), console.time(), console.trace()
• No console.assert() — use an if guard with console.error
• Stack traces from console.error are not automatically included — pass err.stack explicitly
• The log level prefix is fixed by the runtime, not configurable from JS