writing a simple helper module

[espruino-discuss]

Posted at 2018-01-28 by @MaBecker

The plan is to write a module and include it in custom build with JSMODULESOURCES to have all nice tools in place without wasting time on load.

Starting with a time helper as sample, I was fiddling around and have no clue how to write a working module. Any suggestions how to make this work?

// module code  jstools.js

var jstools = function (){};

jstools.prototype.setTimeByUrl = function(url,tz,callback) {
	require('http').get(url, function(res){
    	var date = new Date(res.headers.Date);
    	if (date > 0 ) {
      		setTime(date/1000);
      		E.setTimeZone(tz);
      		error = null;
    	} else {
      		error = 'no date';
  		}
  		if (callback)
  			callback(error);
	});
};

exports = jstools;

// test code 
var jstools = require('jstools');

setTimeout(function(){
  jstools.setTimeByUrl('http://www.espruino.com',1,function(e){console.log(e);});
},1000);

//output 
Uncaught Error: Function "setTimeByUrl" not found!
 at line 1 col 9
jstools.setTimeByUrl('http://www.espruino.com',1,function(e)...
        ^
in function called from system
 

[espruino-discuss]

Posted at 2018-01-28 by PaddeK

Hmm first guess is you need to create an instance of your jstools "class" with new.

var JsTools = require('jstools');

var jt = new JsTools();

setTimeout(function() {
    jt.setTimeByUrl('http://www.espruino.com', 1, console.log);
}, 1000);

Not tested... but should work :)

[espruino-discuss]

Posted at 2018-01-28 by @MaBecker

thanks for your suggestion, this is the output

Uncaught Error: Function "setTimeByUrl" not found!
at line 1 col 4
jt.setTimeByUrl('http://www.espruino.com', 1, console.log);
^
in function called from system

[espruino-discuss]

Posted at 2018-01-28 by PaddeK

Oh i made a mistake.. try to change the require statement to this..

var JsTools = require('./jstools');

If the module is in the same directory of course. Important point is to provide the path (absolut or relative) to the module.

[espruino-discuss]

Posted at 2018-01-28 by @MaBecker

Thanks, just got it.

just export each function and that's it.

// module jtools.js
exports.setTimeByUrl = function(url,tz,callback) {
	require('http').get(url, function(res){
    	var date = new Date(res.headers.Date);
    	if (date > 0 ) {
      		setTime(date/1000);
      		E.setTimeZone(tz);
      		error = null;
    	} else {
      		error = 'no date';
  		}
  		if (callback)
  			callback(error);
        });
};

// test module jtools.js
var jt = require('jstools');
jt.setTimeByUrl('http://www.espruino.com',1,function(e){console.log(e);});

and no more erros :)

[espruino-discuss]

Posted at 2018-01-28 by PaddeK

Exporting each function removes the need to instantiate with new but should not change the mistake i made with the require. Very Strange.. but glad it works now :)

[espruino-discuss]

Posted at 2018-01-28 by @MaBecker

The require('jstools') works because working with the WebIDE and store the jstools.js file in the module directory of my working project.

[espruino-discuss]

Posted at 2018-01-28 by PaddeK

Ah this explains it.. i develop my modules in a IDE and serve them via a server on localhost.
Then i require them via URL when i want to test them in the WebIDE.

[gfwilliams]

Posted at 2018-01-29 by @gfwilliams

There's some info on making modules here: http://www.espruino.com/Writing+Modules

It's for the website, but that way of working can go equally well when trying to build a module in.

But yes, the main thing is anything you want to access directly should just be exports.xyz = ....

One other thing to note: If you're trying to do arrays in a built-in module, try and do them inside a function where possible:

exports.getMyArray = function() { return [....] }; stores the function text in flash until it's executes, but exports.myArray = [....]; will put the array in RAM as soon as you first call require(...) and will keep it there