javascript - calling callback with parameter

Question

I'm trying to to run a script that will wait for 1 second between loop calls. but the code won't recognize the i parameter.

      for (var i = 0; i < lines.length; i++) {
          var scanProgressInterval = setInterval(function(i) {
          // Process the line, noting it might be incomplete.
            if (lines[i].indexOf("(y/n)") > -1) {
              console.log("includes  (y/n)");
              ws.emit('scan', JSON.stringify({scan: false, question: lines[i]}));
            }
            else if (lines[i].indexOf("any key") > -1) {
              console.log("any key");
              ws.emit('scan', JSON.stringify({scan: false, key: lines[i]}));
            }
          }, 1000);
      }

what's wrong with this code?

Why not use setTimeout with an external counter and repeat it until the counter reaches 0 or 1000 or whatever? Don't overcomplicate your life. It's already complicated enough. — Azamantes
– Azamantes, Commented Oct 18, 2016 at 9:32
setInterval(function(i) { .......... }, 1000, i); this will pass the parameter i to the setInterval function — Shwetha
– Shwetha, Commented Oct 18, 2016 at 9:34

Rishabh · Accepted Answer · 2016-10-18 09:42:43Z

1

Here 'i' is globally declared.

Try using your function as a closure.

      function scanProgressInterval(i){ 
          setInterval(function() {
              // Process the line, noting it might be incomplete.
                if (lines[i].indexOf("(y/n)") > -1) {
                  console.log("includes  (y/n)");
                  ws.emit('scan', JSON.stringify({scan: false, question: lines[i]}));
                }
                else if (lines[i].indexOf("any key") > -1) {
                  console.log("any key");
                  ws.emit('scan', JSON.stringify({scan: false, key: lines[i]}));
                }
              }, 1000);
      }

     for (var i = 0; i < lines.length; i++) {
          scanProgressInterval(i);
      }

answered Oct 18, 2016 at 9:42

Rishabh

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Comments

user7028020 · Accepted Answer · 2016-10-18 09:32:50Z

0

You have to add the params behind the timout:

setInterval(function,milliseconds,param1,param2,...)

Look here for more information.

answered Oct 18, 2016 at 9:32

user7028020

Comments

Rax Weber · Accepted Answer · 2016-10-18 09:37:56Z

0

Your i here: setInterval(function(i) {... is in the scope of the setInterval() function, which means that it has no value because when the callback function is called inside the setInterval() function, it will have no argument passed.

You don't need to put the i as parameter of the callback in setInterval(). Simply remove it because you can already access i within the loop itself.

edited Oct 18, 2016 at 9:37

answered Oct 18, 2016 at 9:32

Rax Weber

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