Javascript for loop nested iteration

Question

I'm trying to iterate through a large array of values and collect an average of one of the values for each second. I can't get this code to work properly, and as far as I can see the issue is with the nested while loop. am I making a scope error that's preventing me from iterating the for loop index?

The data is a timestamp in ms and a radiation count. a.data[i][0] is the timestamp and a.data[i][26] is the count.

for (i = 0; i < a.data.length; i++){
 // counts is the count of radiation over the last timeframe
 var counts = 0;
 // t1 is the start time 
 // t2 is the current iteration time
 var t1, t2 = a.data[i][0];
 while ((t2 - t1) < 1000){
 t2 = a.data[i][0];
 counts += a.data[i][26];
 i++;
 }
 // Geiger Data is an array of { x:(time), y:(value)} datapoints.
 GeigerData.push({x: (t1/1000), y: counts});
}

Answer 1

You problem stems from this line:

 var t1, t2 = a.data[i][0];

Defining JS variables doesn't work like that, and in your code t1 is always undefined. What you really want is

 var t1 = a.data[i][0];
 var t2 = t1;

• Jonathan Crowe: This could also be done var t1 = t2 = a.data[i][0]
• nmarsh: @JonathanCrowe - technically, yes, you could do that, but you super don't want to. Your code is the same as doing this: var t1 = a.data[i][0]; t2 = t1; This puts t2 in the global scope, by not using var. See this fiddle: jsfiddle.net/ucyewprL