validate.js - Yatate

Plain JavaScript, run via flutter_js. Optional - only needed for checks that compare multiple fields against each other; a form's own required/min/max/regex rules (see the Form Editor) already cover single-field validation. Edited via the Script Editor. Runs after those static rules pass and before process.js - see the full processing pipeline.

APIs available

Name	Type	Meaning
`inputs`	object	The submitted values, keyed by field id. Each script runs in its own isolated context, so writing to it here has no effect anywhere else.
`errors`	object	Write validation messages into it. Its final state when the script finishes is what matters - the return value is ignored.

if (inputs.sale_price <= 0) {
  errors["sale_price"] = "Sale price must be greater than zero.";
}
if (inputs.year < 1900 || inputs.year > new Date().getFullYear() + 1) {
  errors["year"] = "Enter a valid model year.";
}

Field errors vs. general errors

errors["field_id"] - shows inline under that field. The key must match a real field id.
Any other key - e.g. errors["main"] = "At least 4 options are required"; - doesn't match a field id, so it shows instead as a form-level banner above the fields. Use as many distinct non-field keys as you need to report more than one general message; each key holds a single string, not an array (errors.main.push(...) doesn't work - errors is a plain object).
Leave errors completely untouched when there's nothing to report.

Writing anything to errors - field-specific or general - stops the submission there; process.js doesn't run.