Field modules

Calculations ​

Calculations evaluates a formula from other field values and writes the result into a read-only input.

Events ​

The formie:field:calculations:before-evaluate event ​

Triggered right before the formula is evaluated.

js
document.addEventListener('formie:field:calculations:before-evaluate', (event) => {
  const { calculations, variables } = event.detail;

  // Treat a blank discount field as zero before the formula runs.
  if (calculations?.dataset.formieInputId === 'quoteTotal' && variables.discount === '') {
    variables.discount = 0;
  }
});

The formie:field:calculations:after-evaluate event ​

Triggered after the formula is evaluated and before the result is written back into the input.

js
document.addEventListener('formie:field:calculations:after-evaluate', (event) => {
  // Format numeric results for display without changing the source fields.
  if (typeof event.detail.result === 'number') {
    event.detail.result = event.detail.result.toFixed(2);
  }
});

The broader module lifecycle also includes scoped events such as formie:module:calculations:after-setup.

Last updated: May 6, 2026, 3:46 PM
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