Import: collection

The collection import provides helpers for working with maps and lists.

filter

filter(items, predicate)

Calls predicate for each element in collection, returning a list of elements that the predicate does return true for.

Arguments

Name	Description
items	the list or map to perform the filter against.
predicate	a predicate function to call for each element in the collection. A response of `true` will add the element to the result list.

Examples

Return all even numbers:

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find

find(items, predicate)

Find and return an element within a collection according to the provided predicate. If nothing is found, returns undefined.

Arguments

Name	Description
items	the list or map to perform the find against.
predicate	a predicate function to call for each element in the collection. A response of `true` will return the element and complete the find.

Examples

Find an element in a collection based on its value:

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Find an element in a collection based on its key:

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matches

matches(items, partial)

Compare each element in a collection against a partial map using deep comparison. Returns the list of elements that returned true for the partial comparison. If no matches are found, returns an empty list.

Arguments

Name	Description
items	the list or map to perform the match against.
partial	the map used for partial deep comparison against each element in the collection.

Examples

Return all items that contain {"foo": {"bar": "wip"}}:

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reduce

reduce(items, accumulator[, initial])

Call an accumulator function for each element in collection, supplying the previous accumulated value as the accumulation parameter.

Arguments

Name	Description
items	the list or map to perform the reduce against.
accumulator	a function that is called for each element in the collection, used to accumulate the value. The first argument is the current accumulated value, the remaining arguments use the same rules as predicate functions.
initial	the initial value to use. It is an optional argument, and if not provided the first element in the collection is used as the initial value.

Examples

Reduce the collection by adding each element together:

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reject

reject(items, predicate)

Calls predicate for each element in collection, returning a list of elements that the predicate does not return true for.

Arguments

Name	Description
items	the list or map to perform the reject against.
predicate	a predicate function to call for each element in the collection. A response of `false` will add the element to the result list.

Examples

Return all odd numbers by rejecting even ones:

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Predicates

Some helpers accept a predicate function, which has the purpose of making an assertion. Each predicate may accept differing arguments and return differing types. If the collection is a list, the parameters will be the element and index. If the collection is a Map, the parameters will be the value and the key.

Examples

A predicate for a list of items:

// including index
func(item, index) {
  return true
}

// excluding index
func(item) {
  return true
}

A predicate for a map of items:

// including key
func(value, key) {
  return true
}

// excluding key
func(value) {
  return true
}