Redact PII from Google Analytics (GTM)

redact-pii-from-ga.js

// from https://brianclifton.com/blog/2017/09/07/remove-pii-from-google-analytics/
function() {
    return function(model) {
	// Add the PII patterns into this array as objects
	var piiRegex = [
      	      {
	    		name: 'EMAIL',
	    		regex: /\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b/gi,
	    		group: ''
		    },{
			    name: 'TEL',
			    regex: /((tel=)|(telephone=)|(phone=)|(mobile=)|(mob=))[\d\+\s][^&\/\?]+/gi,
			    group: '$1'
			},{
			    name: 'NAME',
			    regex: /((firstname=)|(lastname=)|(surname=))[^&\/\?]+/gi,
			    group: '$1'
			},{
			    name: 'PASSWORD',
			    regex: /((password=)|(passwd=)|(pass=))[^&\/\?]+/gi,
			    group: '$1'
			},{
			    name: 'ZIP',
			    regex: /((postcode=)|(zipcode=)|(zip=))[^&\/\?]+/gi,
			    group: '$1'
			},{
			    name: 'ADDRESS',
			    regex: /((address(\d)?=)|(street=))[^&\/\?]+/gi,
			    group: '$1'
			}
		       ];
	// Fetch reference to the original sendHitTask
	var originalSendTask = model.get('sendHitTask');
	var i, hitPayload, parts, originalHitPayLoad, val;
	// Overwrite sendHitTask with PII purger
	model.set('sendHitTask', function(sendModel) {
	    hitPayload = sendModel.get('hitPayload').split('&');
	    originalHitPayLoad = sendModel.get('hitPayload').split('&');
	    try {
		for (i = 0; i < hitPayload.length; i++) {
		    parts = hitPayload[i].split('=');
		   // Double-decode, to account for web server encode + analytics.js encode
        	try {
          		val = decodeURIComponent(decodeURIComponent(parts[1]));
        	} catch(e) {
          		val = decodeURIComponent(parts[1]);
        	}  
            //val = decodeURIComponent(unescape(parts[1]));
		    piiRegex.forEach(function(pii) {
			val = val.replace(pii.regex, pii.group + '[REDACTED ' + pii.name + ']');
		    });
		    parts[1] = encodeURIComponent(val);
		    hitPayload[i] = parts.join('=');
		}
		sendModel.set('hitPayload', hitPayload.join('&'), true);
		originalSendTask(sendModel);	
	    }

	    catch(err) {
		console.log("Error found: " + err.message);
		hitPayload = sendModel.get('hitPayload');
		sendModel.set('hitPayload', originalHitPayLoad, true);
		originalSendTask(sendModel);
	    }
	});
    }
}