A fantastic explanation.
On Tuesday, November 27, 2012 3:17:14 AM UTC+11, Charles Care wrote:
>
> Hi Dave,
>
> The callback-based APIs follow a convention where the first positional
> parameter is for error information. You're asking the Node 'fs' library to
> read 'file1.txt'. If the read is successful, then the 2nd param ('data')
> will contain a representation of the file's contents, and the 1st param
> will be null. Alternatively, if an error occurs, then the err parameter
> will have a value representing the error, and the 2nd param will be either
> null or undefined.
>
> The parameter names are a convention: you could call them 'apple' and
> 'orange', but that would really make your code hard to maintain!
>
> Hope that helps,
>
> Charles
>
> On 26 November 2012 15:50, Dave Johnson <[email protected]<javascript:>
> > wrote:
>
>> Hello and I apologise if this is a stupid question but I am reading up on
>> Callbacks in node.js and wanted to ask something about it.
>>
>> Example code:
>>
>> fs.readFile('file1.txt', 'utf8', function (err, data) {
>> if (err) throw err;
>> console.log('File 1 read!');
>> });
>>
>> I just dont know what the parameters *err* & *data* are, is this
>> something that the node.js engine resolves internally? Hope I am making
>> sense, in other coding you would create these variables and then pass them
>> to a method.
>>
>> Thanks,
>>
>> Dave Johnson
>>
>>
>
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