Regex matching for date range

Question

Say I have a have a date range in a format like 1390573112to1490573112, where the numbers are epoch unix time. Is there a way to use regex to validate that the second number is greater than the first?

Answer 1

Edit: I just noticed that you never specified your language of choice to be JavaScript. Do you have a particular language that you are using? As dawg mentioned it's not reflex that will solve this alone.

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Not regex alone, but you could use it to get the numbers and then something like this to compare them:

// Method to compare integers.
var compareIntegers = function(a, b) {
  /* Returns:
   1 when b > a
   0 when b === a
  -1 when b < a
  */
  return (a === b) ? 0 : (b > a) ? 1 : -1;
};

// Method to compare timestamps from string in format "{timestamp1}to{timestamp2}"
var compareTimestampRange = function(str) {
  // Get timestamp values from string using regex
  // Drop the first value because it contains the whole matched string
  var timestamps = str.match(/(\d+)to(\d+)/).slice(1);
  /* Returns:
   1 when timestamp2 > timestamp1
   0 when timestamp2 === timestamp1
  -1 when timestamp2 < timestamp1
  */
  return compareIntegers.apply(null, timestamps);
}

// Test!
console.log(compareTimestampRange('123to456')); // 1
console.log(compareTimestampRange('543to210')); // -1
console.log(compareTimestampRange('123to123')); // 0
console.log(compareTimestampRange('1390573112to1490573112')); // 1

Of course you don't even need regex if your use case is that simple. You could replace this line:

var timestamps = str.match(/(\d+)to(\d+)/).slice(1);

With this:

var timestamps = str.split('to');

to achieve the same result