then
Enables you to work with the subject yielded from the previous command.
Note: .then()
assumes you are already familiar with core concepts such as
closures.
Note: Prefer .should()
with callback over
.then()
for assertions as they are automatically rerun until no assertions
throw within it but be aware of differences.
Syntax
.then(callbackFn)
.then(options, callbackFn)
Usage
Correct Usage
cy.get('.nav').then(($nav) => {}) // Yields .nav as first arg
cy.location().then((loc) => {}) // Yields location object as first arg
Arguments
options (Object)
Pass in an options object to change the default behavior of .then()
.
Option | Default | Description |
---|---|---|
timeout | defaultCommandTimeout | Time to wait for .then() to resolve before timing out |
callbackFn (Function)
Pass a function that takes the previously yielded subject as its first argument.
Yields
Whatever is returned from the callback function becomes the new subject and will
flow into the next command (with the exception of undefined
or null
).
- If the return value is a chain of Cypress commands (eg
return cy.get('button')
), Cypress will wait for them to resolve and use their return value as the new subject. - If the return value is a Promise, Cypress will wait for it to resolve, and use the resolved value as the new subject to continue the chain of commands.
- If the callback returns
undefined
ornull
(or there is no return value), the result of the last Cypress command in the callback function will be yielded as the new subject instead, and flow into the next command. - If the callback returns
undefined
ornull
(or there is no return value) and the callback does not call any Cypress commands, the subject will not be modified, and the previous subject will carry over to the next command.
The callback function of .then()
is not retried. It is
unsafe to return
DOM elements directly from the callback and then use further commands on them.
Instead, use Cypress queries to locate the elements you're interested in acting
or asserting on.
Examples
We have several more examples in our
Core Concepts Guide which go into
the various ways you can use .then()
to store, compare, and debug values.
DOM element
button
element is yielded
The cy.get('button').then(($btn) => {
const cls = $btn.attr('class')
cy.wrap($btn).click().should('not.have.class', cls)
})
The number is yielded from previous command
cy.wrap(1)
.then((num) => {
cy.wrap(num).should('equal', 1) // true
})
.should('equal', 1) // true
Change subject
The el subject is changed with another command
cy.get('button')
.then(($btn) => {
const cls = $btn.attr('class')
cy.wrap($btn).click().should('not.have.class', cls).find('i')
// since there is no explicit return
// the last Cypress command's yield is yielded
})
.should('have.class', 'spin') // assert on i element
The number subject is changed with another command
cy.wrap(1).then((num) => {
cy.wrap(num)).should('equal', 1) // true
cy.wrap(2)
}).should('equal', 2) // true
The number subject is changed by returning
cy.wrap(1)
.then((num) => {
cy.wrap(num).should('equal', 1) // true
return 2
})
.should('equal', 2) // true
undefined
will not modify the yielded subject
Returning cy.get('form')
.then(($form) => {
console.log('form is:', $form)
// undefined is returned here, but $form will be
// yielded to allow for continued chaining
})
.find('input')
.then(($input) => {
// we have our $input element here since
// our form element was yielded and we called
// .find('input') on it
})
Raw HTMLElements are wrapped with jQuery
cy.get('div')
.then(($div) => {
return $div[0] // type => HTMLDivElement
})
.then(($div) => {
$div // type => JQuery<HTMLDivElement>
})
Promises
Cypress waits for Promises to resolve before continuing
Example using Q
cy.get('button')
.click()
.then(($button) => {
const p = Q.defer()
setTimeout(() => {
p.resolve()
}, 1000)
return p.promise
})
Example using bluebird
cy.get('button')
.click()
.then(($button) => {
return Promise.delay(1000)
})
Example using jQuery deferred's
cy.get('button')
.click()
.then(($button) => {
const df = $.Deferred()
setTimeout(() => {
df.resolve()
}, 1000)
return df
})
Notes
Differences
What's the difference between .then()
and .should()
/.and()
?
Using .then()
allows you to use the yielded subject in a callback function and
should be used when you need to manipulate some values or do some actions.
When using a callback function with .should()
or .and()
, on the other hand,
there is special logic to rerun the callback function until no assertions throw
within it. You should be careful of side affects in a .should()
or .and()
callback function that you would not want performed multiple times.
Rules
Requirements
-
.then()
requires being chained off a previous command.
Assertions
-
.then()
will only run assertions you have chained once, and will not retry .
Timeouts
-
.then()
can time out waiting for a promise you've returned to resolve.
Command Log
.then()
does not log in the Command Log
History
Version | Changes |
---|---|
0.14.0 | Added timeout option |
< 0.3.3 | .then() command added |