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up.form up.observe(elements, [options], onChange)
JavaScript function

This feature has been deprecated. Use up.watch() instead.

Load unpoly-migrate.js to polyfill deprecated features.

Observes form fields and runs a callback when a value changes.

Example

The following would print to the console whenever an input field changes:

up.observe('input.query', function(value) {
  console.log('Query is now %o', value)
})

Parameters

elements
required

The form fields that will be observed.

You can pass one or more fields, a <form> or any container that contains form fields. The callback will be run if any of the given fields change.

Type: string | Element | Array<Element> | jQuery
[options.batch=false]
optional

If set to true, the onChange callback will receive multiple detected changes in a single diff object as its argument.

Type: boolean
[options.delay=up.form.config.observeDelay]
optional

The number of milliseconds to wait before executing the callback after the input value changes. Use this to limit how often the callback will be invoked for a fast typist.

Type: number
onChange
required

The callback to run when the field's value changes.

If given as a function, it receives two arguments (value, name). value is a string with the new field value and name is the name of the form field that changed. If given as a string, it will be evaled as JavaScript code in a context where (value, name) are set.

A long-running callback function may return a promise that settles when the callback completes. In this case the callback will not be called again while it is already running.

Type: Function(value, name): string

Return value

A destructor function that removes the observe watch when called.

Type: Function()