Map field-name to checkbox

The + sign is used to easily convert a field value to a number explicitly, which is usually only done when the value will be used later in the script as a number, as when summing the values from several fields. (Blank fields values are returned as empty stings.) In this case, you're using the value as a string, so you should not only remove the +, but you should use the valueAsString property instead of the value property, something like:

if (event.valueAsString == "Text") this.getField("Text1 Checkbox").checkThisBox(0, True);

This will ensure that it always works. Note that the following would not:

if (event.value == "012345") this.getField("Text1 Checkbox").checkThisBox(0, True);

if the user entered "012345" since the leading zero would not be included when the result is automatically cast as a number and then compared to a string. It would work when using the valueAsString property.

Why did you add a plus-symbol before event.value? Do you know what that means?