for loop

[espruino-discuss]

Posted at 2014-04-09 by Sacha

Hi Gordon,

This for loop throws an error:

for(i=0,j=7;i<10;i++,j++) { console.log('a'); }
ERROR: Got ',' expected ')' at line 1 col 22
for(i=0,j=7;i<10;i++,j++) { console.log('a'); }
^

Is working on jconsole.com.

http://jsconsole.com/?for(i%3D0%2Cj%3D7%3Bi%3C10%3Bi%2B%2B%2Cj%2B%2B)%20%7B%20console.log(%27a%27)%3B%20%7D

Greetings

Sacha

[gfwilliams]

Posted at 2014-04-10 by @gfwilliams

Hmm - thanks. It should be an easy fix.

[gfwilliams]

Posted at 2014-04-10 by @gfwilliams

Ok - fixed for 1v61 :)

[espruino-discuss]

Posted at 2014-04-10 by Sacha

Thank you.

[espruino-discuss]

Posted at 2014-10-09 by user49129

If a js code breaks from a for loop as follows, the loop index i should not be changed!

for(var i=0; i<10; i++) if(i==3)break; console.log(i)

[gfwilliams]

Posted at 2014-10-09 by @gfwilliams

Thanks for letting me know. I've just fixed this, so it'll be in the 1v71 release of Espruino.

[espruino-discuss]

Posted at 2015-08-20 by bigplik

do you know how to use this for loop similar to way like Arduino ?
eg.

for(int i=0 ; i<10 ; i++){
    digitalWrite(13, HIGH);
    delay(500);
    digitalWrite(13, LOW);
    delay(500);
}

I was trying to use tutorial from buttons example, and change it a bit, like when I press the button LED1 will blink let say twice or triple times, in arduino modification it is easy, how to do it in espruino?

[espruino-discuss]

Posted at 2015-08-20 by fdufnews

Delay is not a good way to manage time dependant tasks as it uses all the resources for itself
You can do it this way:

var maxTime = 500;
var maxStep = 10;
var count = 0;
var timer;
var state = false;
var blinkActive = false;

function blink(){
  state = !state;
  digitalWrite(LED1,state);
  if (!state) count--;
  if (count===0){
    clearInterval(timer);
    blinkActive = false;
  }
}

function launchBlink(){
  if(blinkActive === false){
    count = maxStep;
    timer = setInterval(blink,maxTime);
    blinkActive = true;
  }
}

function onInit(){
  clearInterval();
  LED1.write(0);
  setWatch(launchBlink,BTN,{repeat: true, edge: 'rising', debounce: 100});
}

onInit();

[espruino-discuss]

Posted at 2015-08-20 by DrAzzy

delay() is a scourge upon Arduino, and a plague that we are largely free from over here in Espruino-land. delay() is horribly overused on Arduino, and it's only simpler for very basic cases - as soon as you start making things more complicated, you end up in a mess.

We have modern, sensible tools for non-blocking delays - setInterval(), setTimeout(), and setWatch() (for reacting to a pin change).

All of those tasks on Arduino would either block, or require a "blinkWithoutDelay" type approach

unsigned long lastBlink=0;
unsigned long turnOnLedAt=30000;
byte led1st=0;
byte led2st=0;
#define ledpin 13 
#define ledpin2 14 //note that there's no led connected here on normal arduino board

void loop() {
if (millis()+500 > lastBlink) {
led1st=!led1st;
digitalWrite(ledpin,led1st);
}
if (millis>turnOnLedAt && led2st==0) {
led2st=1;
digitalWrite(ledpin2,led2st);
}
}

vs Espruino:

ledpin1 = LED1;
ledpin2 = LED2;
var ledst=0;
function onInit () {
setTimeout("digitalWrite(ledpin2)",30000); 
setInterval("ledst=!ledst;digitalWrite(ledpin1,ledst);",500);
}

or

var ledst=0;
ledpin1 = LED1;
ledpin2 = LED2;
function onInit () {
setTimeout(function() {digitalWrite(ledpin2);},30000); 
setInterval(function() {ledst=!ledst;digitalWrite(ledpin1,ledst);},500);
}

[espruino-discuss]

Posted at 2015-08-20 by bigplik

it's working, now I have equivalent to for loop operations ;), thank you fdufnews
DrAzzy, your code generate some error

[espruino-discuss]

Posted at 2015-08-20 by fdufnews

Thanks!

note that I have made a small correction to the code in order to prevent double launch of the blink sequence if it is already active.

[espruino-discuss]

Posted at 2015-08-20 by bigplik

cool, I had some counting problem when disconnected and connected board again, everything was working till I didn't use "save()" command and turned board off and back on, or disconnected and connected again, will check how it is going on now ;)

fdufnews - everything is workin now, even after power of and on again the board,
very helpful ;)

[espruino-discuss]

Posted at 2015-08-20 by DrAzzy

I fixed the code so it runs out of the box now - I had just omitted the definitions for the ledpin1/ledpin2 variables because I was illustrating how to write the code (just like how in the Arduino example, I didn't include definitions for the LED pins).

I also missed the second argument to digitalWrite() in one case.

Note that sometimes when copy/pasting code from these forums, it inserts non-printing junk characters. These get red-marked in the IDE, remove them where they appear.

[espruino-discuss]

Posted at 2015-08-20 by bigplik

DrAzzy, thank you, your code is also working now ;)