Generator and Iterator manipulation

eater.js

/**
 * Eater.js version: 0.2.0
 * Usage examples: 
 * // Even squares of numbers between 1-10
 *   _(_.filter( x => x % 2 === 0, _.map(x => x * x, _.range(1, 10))))
 * // 10 coin flips
 *   _(_.take(10, _.map(n => n < 0.5, _.func(Math.random))))
 * // first 100 Fibonacci numbers (assuming already defined generator)
 *   _(_.take(100, fibonacci()))
 * // Convert pseudo-array to array
 *   _(_({ 0: 1, 1: 2, length: 2} ))
 */
window._ = window.eater = (function(){'use strict';
function eater(it) {
  if(typeof it === 'function') {
    return eater.func(it);
  } else if(it.next) {
    return eater.take(it);
  } else if(typeof it.length === 'number') {
    return eater.loop(it);
  } else if(it[Symbol.iterator]) {
    return [...it];
  } else if(it.next) {
    return eater.take(it);
  } else {
    return eater.fill(it);
  }
}
Object.assign(eater, {
  /* Creators */
  *range(start = Infinity, end = null) {
    if(end == null) {
      [start, end] = [1, start];
    }
    for(var i = start; i <= end; i++) {
      yield i;
    }
  },
  *fill(val) {
    while(true) {
      yield val;
    }
  },
  *func(fn, ...args) {
    while(true) {
      yield fn(...args);
    }
  },
  *loop(it) {
    for(var i = 0; i < it.length; i++) {
      yield it[i];
    }
  },
  *join(...its) {
    for(var it of its) {
      yield* it;
    }
  },
  /* Accessors */
  *take(amt, iter) {
    if(iter == null) {
      iter = amt;
      amt = Infinity
    }
    var it = iter[Symbol.iterator] ? iter[Symbol.iterator]() : iter
    for(var i = 0, n; i < amt && !((n = it.next()).done); i++) {
      yield n.value;
    }
  },
  *each(fun, it) {
    for(var i of it) {
      fun(i);
      yield i;
    }
  },
  get(it) {
    return it.next().value;
  },
  /* Manipulators */
  *map(fun, it) {
    for(var i of it) {
      yield fun(i);
    }
  },
  *filter(fun, it) {
    for(var i of it) {
      if(fun(i)) {
        yield i;
      }
    }
  }
});
return eater;
})();