Core Pull Functions

Core functions to create and run Pull Lines.

composeOperations

composeOperations(operations) => PullOperation

Composes several existing operations into a new one.

import { composeOperations, pullArray, flattenArrays, zip } from "@undercut/pull";
function interleave(...sources) {    const operations = [        zip(...sources),        flattenArrays()    ];
    return composeOperations(operations);}
const source = [1, 3, 5];const pipeline = [    interleave([2, 4, 6])];
const result = pullArray(pipeline, source);
console.log(result); // [1, 2, 3, 4, 5, 6]

pull

pull(target, pipeline, source) => TargetReturnValue

Executes the pipeline by pulling items from the source to the target and returns target's return value.

import { pull, filter, map, skip, toArray } from "@undercut/pull";
const source = [1, 2, 3, 4, 5, 6, 7];const pipeline = [    skip(2),    filter(x => x % 3),    map(x => x * 2)];
const result = pull(toArray(), pipeline, source);
console.log(result); // [8, 10, 14]

pullArray

pullArray(pipeline, source) => Array

Same as pull, but target is implicitly set to toArray().

import { pullArray, filter, map, skip } from "@undercut/pull";
const source = [1, 2, 3, 4, 5, 6, 7];const pipeline = [    skip(2),    filter(x => x % 3),    map(x => x * 2)];
const result = pullArray(pipeline, source);
console.log(result); // [8, 10, 14]

pullLine

pullLine(pipeline, source) => Iterable

Creates a Pull Line (Iterable).

Useful when you want to pass it somewhere or being able to re-evaluate the result again in the future.

import { pullLine, append, compact, skip } from "@undercut/pull";
const source = [0, 1, 2, 3];const pipeline = [    append(4, 5),    compact(),    skip(2)];
const myItems = pullLine(pipeline, source); // No evaluation happens at this step.
const result1 = Array.from(myItems);
console.log(result1); // [3, 4, 5]
source.push(7); // Modify the source and re-evaluate. Pull Line has a reference to the source.
const result2 = Array.from(myItems);
console.log(result2); // [3, 7, 4, 5]

pullValue

pullValue(pipeline, source) => item

Pulls the first value out of the pipeline. It's like pull with target set to the head utility.

import { pullValue, filter, map, skip } from "@undercut/pull";
const source = [1, 2, 3, 4, 5, 6, 7];const pipeline = [    skip(2),    filter(x => x % 3),    map(x => x * 2)];
const result = pullValue(pipeline, source);
console.log(result); // 8