iterama/node/skip.js

Composable functional (async) iterable helpers

var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.skip = void 0;

var _circularr = _interopRequireDefault(require("circularr"));

var _iterate = require("./iterate");

const skipFirst = n => iterable => ({
  *[Symbol.iterator]() {
    const iterator = (0, _iterate.iterate)(iterable);
    let i = 0;

    while (i < n && !iterator.next().done) {
      i++;
    }

    for (const value of iterator) {
      yield value;
    }
  }

});

const skipLast = n => iterable => ({
  *[Symbol.iterator]() {
    const iterator = (0, _iterate.iterate)(iterable);
    const last = new _circularr.default(n);

    for (let i = 0; i < n; i++) {
      const result = iterator.next();

      if (result.done) {
        break;
      }

      last.shift(result.value);
    }

    for (const value of iterator) {
      yield last.shift(value);
    }
  }

});

const skip = n => n < 0 ? skipLast(-n) : skipFirst(n);

exports.skip = skip;