Referencesingle
Reference · 99
single
single
Expects exactly one matching value.
Signature
single(predicate?: (value: T, index: number) => boolean): OperatorFunctionWhat it does
Emits a value only if source contains exactly one matching element. If there are zero or more than one, it fails with an error.
When to use
Invariants: there must be exactly one selected user, exactly one primary item, exactly one result.
Gotcha
For "the first match", use first/find. single checks uniqueness and can throw an error.
See also
first, find
script.ts
CONSOLE · Console output
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