Skip to main content

map()

map<Input, Output, ErrorOutput>(mapper, errorMapper?): OperatorFunction<Input, Output | ErrorOutput>

Defined in: src/Map.ts:31

Creates an operator that transforms every item with mapper.

If mapper throws and an errorMapper is given, the value returned by errorMapper is emitted instead and the iteration continues. Without an errorMapper the error is rethrown to the consumer.

Type Parameters​

Input​

Input

Output​

Output

ErrorOutput​

ErrorOutput = never

Parameters​

mapper​

(input) => Output | Promise<Output>

transforms an item; may be asynchronous

errorMapper?​

(input, error) => ErrorOutput | Promise<ErrorOutput>

turns an error thrown by mapper into a value; may be asynchronous

Returns​

OperatorFunction<Input, Output | ErrorOutput>

an operator function

Example​

const result = await chain([1, 2, 3])
    .map(
        (n) => {
            if (n === 2) {
                throw new Error("two");
            }
            return n * 10;
        },
        (n) => -n,
    )
    .toArray();
// => [10, -2, 30]