Find
A find operation searches a collection for the first element or entry matching a value or predicate and returns it, or indicates that no match exists.
Secrets of the JavaScript Ninja, Second Edition
An Array method that returns the first element passing a callback test, or undefined if none does.
- How it is used
- Finds the first array item that satisfies a callback condition.
- How deep it goes
- Explains callback-based matching and the `undefined` no-match result, without detailing implementation internals.
- Examples
- Finds the ninja wielding a wakizashi and checks for a katana match that yields `undefined`.
- What you can do after
- Apply `find` with a callback to retrieve the first matching array item or detect that none matches.
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C++ Concurrency in Action, Second Edition
`std::find` is a C++ standard library algorithm that returns the first element in a range equal to a specified value, or the end of the range if none is found.
- How it is used
- Uses early completion to guide the design of parallel search.
- How deep it goes
- Explains early completion and atomic cancellation through a parallel implementation.
- Examples
- Uses an attic photograph search and a four-thread comparison to illustrate early completion.
- What you can do after
- Evaluate when parallel search can lose to serial search and use a flag to signal a found match.
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Clojure: The Essential Reference
find is a Clojure function that searches an associative collection for a key and returns the corresponding key-value entry or nil.
- How it is used
- Searches associative collections when the complete key-value entry, rather than only its value, is needed.
- How deep it goes
- Defines inputs, outputs, supported collections, edge cases, and entry extraction, but does not develop implementation internals.
- Examples
- Demonstrates map entries, vector indexes, subvectors, missing keys, and filtering records with keep.
- What you can do after
- Apply it via Clojure to locate entries, extract keys or values, and retain matching records without exceptions for absent keys.
The Well-Grounded Rubyist, Fourth Edition
find, also known as detect, is an Enumerable method that returns the first element for which its block evaluates truthily, or nil when no element matches.
- How it is used
- Searches an enumerable collection for one matching element using a block-defined selection criterion.
- How deep it goes
- Explains block evaluation, early termination, nil ambiguity, fallback Procs, and contrasts with multi-result selectors.
- Examples
- Uses a numeric array search, a nil-element search, a fallback lambda, and a custom Rainbow enumerable.
- What you can do after
- Apply it to return the first matching element, detect absence through nil, or provide a fallback Proc.
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Related concepts
- containsalternative to · Contains is a membership-query operation that reports whether a specified value, key, element, or substring occurs in a container or collection.
- get methodalternative to · A lookup operation on a mapping or associative collection that returns the value associated with a key or index, often with a null-like result or supplied default when no entry exists.
- missing valueproduces · A missing value is a marker or condition indicating that an expected data value or reference is absent, unavailable, unknown, or inapplicable.
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