Function parameter that includes "[," meaning

Question

i've seen this syntax [, everywhere and have no idea what it implies.

 d3.mean(array[, accessor])

.on( events [, selector ] [, data ], handler )

Why is the comma after the opening bracket? What does it mean?

the function parameters that are encased in square brackets are *optional*, omit the brackets from your code. the brackets are only used for documentation purposes. — Glenn Ferrie, Dec 07 '15 at 21:19
See this: http://stackoverflow.com/questions/10925478/how-to-read-api-documentation-for-newbs — Maria Ines Parnisari, Dec 07 '15 at 21:20
Glenn should add the comment as an answer, you know, for the glory and the money...:P — Ernesto, Dec 07 '15 at 21:23

score 4 · Accepted Answer · answered Dec 07 '15 at 21:25

The comma is a separator between parameters. The square brackets mean that the parameter is optional.

So, when you read something like this:

.on( events [, selector ] [, data ], handler )

You can know that you have multiple options of how to call this function:

.on(events, handler)
.on(events, selector, handler)
.on(events, selector, data, handler)

Tobias · Answer 2 · 2015-12-07T21:33:50.983

1

It just means that the parameters are optional.

But be careful! These square brackets are just used in the documentation.

edited Dec 07 '15 at 21:33

answered Dec 07 '15 at 21:21

Tobias

2 Answers2