stdio.markdown

console

Browser-like object for printing to stdout and stderr.

console.log()

Prints to stdout with newline. This function can take multiple arguments in a printf()-like way. Example:

console.log('count: %d', count);

The first argument is a string that contains zero or more placeholders. Each placeholder is replaced with the converted value from its corresponding argument. Supported placeholders are:

• %s - String.
• %d - Number (both integer and float).
• %j - JSON.

If the placeholder does not have a corresponding argument, undefined is used.

console.log('%s:%s', 'foo'); // 'foo:undefined'

If there are more arguments than placeholders, the extra arguments are converted to strings with util.inspect() and these strings are concatenated, delimited by a space.

console.log('%s:%s', 'foo', 'bar', 'baz'); // 'foo:bar baz'

If the first argument is not a format string then console.log() prints a string that is the concatenation of all its arguments separated by spaces. Each argument is converted to a string with util.inspect().

console.log(1, 2, 3); // '1 2 3'

console.info()

Same as console.log.

console.warn()

console.error()

Same as console.log but prints to stderr.

console.dir(obj)

Uses util.inspect on obj and prints resulting string to stderr.

console.time(label)

Mark a time.

console.timeEnd(label)

Finish timer, record output. Example

console.time('100-elements');
for (var i = 0; i < 100; i++) {
  ;
}
console.timeEnd('100-elements');

console.trace()

Print a stack trace to stderr of the current position.

console.assert()

Same as assert.ok().