Question

I have an array with incidents that has happened, that are written in free text and therefore aren’t following a pattern except for some keywords, eg. “robbery”, “murderer”, “housebreaking”, “car accident” etc. Those keywords can be anywhere in the text, and I want to find those keywords and add those to categories, eg. “Robberies”.

In the end, when I have checked all the incidents I want to have a list of categories like this:

Robberies: 14
Murder attempts: 2
Car accidents: 5
...

The array elements can look like this:

incidents[0] = "There was a robbery on Amest Ave last night...";
incidents[1] = "There has been a report of a murder attempt...";
incidents[2] = "Last night there was a housebreaking in...";
...

I guess the best here is to use regular expressions to find the keywords in the texts, but I really suck at regexp and therefore need some help here.

The regular expressions is not correct below, but I guess this structure would work?
Is there a better way of doing this to avoid DRY?

var trafficAccidents = 0,
    robberies = 0,
    ...

function FindIncident(incident) {
    if (incident.match(/car accident/g)) {
        trafficAccidents += 1;
    }
    else if (incident.match(/robbery/g)) {
        robberies += 1;
    }
    ...
}

Thanks a lot in advance!

Answer 1

The following code shows an approach you can take. You can test it here

var INCIDENT_MATCHES = {
  trafficAccidents: /(traffic|car) accident(?:s){0,1}/ig,
  robberies: /robbery|robberies/ig,
  murder: /murder(?:s){0,1}/ig
};

function FindIncidents(incidentReports) {
  var incidentCounts = {};
  var incidentTypes = Object.keys(INCIDENT_MATCHES);
  incidentReports.forEach(function(incident) {
    incidentTypes.forEach(function(type) {
      if(typeof incidentCounts[type] === 'undefined') {
        incidentCounts[type] = 0;
      }
      var matchFound = incident.match(INCIDENT_MATCHES[type]);
      if(matchFound){
          incidentCounts[type] += matchFound.length;
      };
    });
  });

  return incidentCounts;
}

Regular expressions make sense, since you’ll have a number of strings that meet your ‘match’ criteria, even if you only consider the differences in plural and singular forms of ‘robbery’. You also want to ensure that your matching is case-insensitive.

You need to use the ‘global’ modifier on your regexes so that you match strings like “Murder, Murder, murder” and increment your count by 3 instead of just 1.

This allows you to keep the relationship between your match criteria and incident counters together. It also avoids the need for global counters (granted INCIDENT_MATCHES is a global variable here, but you can readily put that elsewhere and take it out of the global scope.