Subtract values in column in JS

Question

I am reading a cvs-file and one column contains unix timestamps. I would like to calculate the difference between value1 and value2, value 2 and value3 et cetera. How should I do this?

Answer 1

See: Javascript code to parse CSV data

Calculating time difference is merely subtracting them once you got the data into an array and parsed them as Number/long with parseInt.

How to convert a String to long in javascript?

Answer 2

Edited code snippet after reading comments. It seems that all differences in the data are 900 mSec, but this code should work for whatever other values.

Thing to note is that it assumes "high to low" ordering as seemingly present in the data.

var csv = [
  '1374225300,126.0,1662.0,379.0,337.0,1091.0,893.0',
  '1374224400,84.0,1491.0,251.0,289.0,909.0,801.0',
  '1374223500,72.0,1200.0,126.0,180.0,651.0,682.0 ',
  '1374222600,84.0,1011.0,126.0,180.0,505.0,563.0 ',
  '1374221700,72.0,718.0,84.0,109.0,295.0,441.0 '
  //... etcetera
];

function getPairDifference( pair ) {
  //"pair" is a zero-based integer.
  // "0" will return a difference between csv rows "0" & "1"
  // "1" will return a difference between csv rows "1" & "2"
  // etcetera...

  var firstVal = parseInt( csv[pair].split(",")[0] );
  var secondVal = parseInt( csv[pair + 1].split(",")[0] );
  return firstVal - secondVal;
}

for ( var i = 0; i < csv.length; i += 1) {
  // Demo code to visualize numbers.
  // Actual function call of interest is simply "getPairDifference( i )"
  $( "<div></div>" ).text( "DIFF "+i+": " + getPairDifference( i ) ).appendTo( "body" );
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>