Text field ‘OnChangeEvent’

[Stephen Abshire]

Greetings,

Is there a way that I can detect when a text field that uses a pick list has had a value change? Say for example it used to be ‘ABC’ and now it is ‘DEF’. How can I catch when the value has changed so I can script it? I suppose a hidden field could be used as a form of global variable but that seems like a hack.

[Brendan]

If you have a Script field and you use record.getFieldValue(field_id) within the script, Tap Forms will add that field_id to a watch list. So when the value of that field changes, the script will execute.

[Stephen Abshire]

The fields involved are all text because they require user input, yet I want to programmatically modify them based upon certain criteria.

[Sam Moffatt]

I use a hidden field to save state of what fields used to be and then compare the new field value against the old one. There is no before change data so you have to grab it yourself.

I also have another technique where with the script field, you can return a value. So you can use the script field itself to store the previous state and by accessing the script field with getFieldValue, you can then get at the previous value. When you finish up your script field, you return the previous value. If you have a few different values you want to track, you can use JSON.stringify and JSON.parse to serialise and unserialise the field value into an object in JSON.

Hopefully that helps.

[Stephen Abshire]

I went with the hidden field method as I wasn’t completely understanding your other method but all good.

[Sam Moffatt]

Reposting because my original reply got flagged as spam.

I’m uploading a sample form template that shows what I mean. It has two fields in it, a text field and a script field. I also included the form logger script with an update that prints out field ID’s in Javascript variable syntax. That’s used at the top top populate the field ID’s because by default the script editor doesn’t expose script fields. I also use this syntax because it includes the form name which makes it easy to keep track of variables in larger documents with lots of forms and lots of fields. There’s a commented line to ensure that Tap Forms registers this script to the field that works even if the line is commented out. I then grab the text field and the contents of the script field.

For the script field, I check to see if it is set and provide a default dictionary if it isn’t set already. If it is set to a value, I assume it’s JSON and parse it back into an object.

Then at that point it’s a quick comparison of the deserialised JSON payload and your new one. I added a message in so you can see a note, always useful after the fact for some of these scripts even if you hide the field by default, you can unhide it to see what it has in it.

Lastly the script field ends with JSON.stringify to return a JSON string as the fields contents. This object can obviously contain what ever you want in it so if you have multiple values instead of setting multiple fields, you just return a value at the end of your field script with the data you need to keep track of from each execution.

Sample execution:

Field script:

// Script Field State
var script_field_state_formID = "frm-86fd53d1f9ab47548636fc2e2d1d0d35";
var script_field_state__main_field_fldID = "fld-2177d4bf8500482d8fc6242faa80c5e6"; // text
var script_field_state__watcher_fldID = "fld-7e997368aef740f68f126d2c8509d148"; // script

// Make sure the field is watched to pick up changes.
//var main_field = record.getFieldValue('fld-2177d4bf8500482d8fc6242faa80c5e6');

var main = record.getFieldValue(script_field_state__main_field_fldID);
var state = record.getFieldValue(script_field_state__watcher_fldID);

if (!state)
{
	state = {'previous':undefined,'message':'Initial setting'};
}
else
{
	state = JSON.parse(state);
}

if (state['previous'] != main)
{
	state['message'] = `Field value changed from '${state['previous']}' to '${main}'`;
	state['previous'] = main;
}

JSON.stringify(state);

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[Stephen Abshire]

Thank you and appreciate the code sample. This is actually what I was working on myself but I was having issues that you answered in another thread regarding setting field values that trigger scripts and using the third parameter of ‘false’ when writing field values. Once again appreciate the help!

[Author]

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