Take two streams, and return a new stream that emits every value from the first stream with the most recent value from the other stream.
var test = require('tape')
var withLatest = require('../')
var S = require('pull-stream')
test('pass null for the default predicate', function (t) {
t.plan(2)
var predicate = null
S(
withLatest.apply(null, [predicate].concat(sources())),
S.collect(function (err, res) {
t.error(err)
t.deepEqual(res, [
[2, 'a'],
[4, 'b'],
[6, 'c']
], 'should combine the streams ok')
})
)
})
test('use predicate function', function (t) {
t.plan(2)
var predicate = function (a, b) {
return { a: a, b: b }
}
S(
withLatest.apply(null, [predicate].concat(sources())),
S.collect(function (err, res) {
t.error(err)
t.deepEqual(res, [
{ a:2, b:'a' },
{ a:4, b:'b' },
{ a:6, b:'c' }
], 'should combine the streams ok')
})
)
})
function sources () {
var sampler = S(
S.values(['a','b','c']),
S.asyncMap(function (ev, cb) {
setTimeout(function () {
cb(null, ev)
}, 210)
})
)
var otherStream = S(
S.values([1,2,3,4,5,6]),
S.asyncMap(function (ev, cb) {
setTimeout(function () {
cb(null, ev)
}, 100)
})
)
return [otherStream, sampler]
}