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Using Generators to lazily build a collection of items in ES6 (babeljs)
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| // Infinitely generate all odd numbers or whatever the MAX Number is | |
| function* oddNumbers() { | |
| let i = 1 | |
| // Infinite loop. But thanks to the yield keyword, we exit this | |
| // loop and return a value. On the next call back in, we resume | |
| // where we left off. | |
| while(1) { | |
| yield i; | |
| // Imagine if this were an expensive computation | |
| i += 2; | |
| } | |
| } | |
| // Materialize n items from the iterable collection and place them | |
| // in a new array | |
| function take(n, iterable) { | |
| let count = 0; | |
| let taken = []; | |
| for (let value of iterable) { | |
| if (count >= n) { | |
| break; | |
| } | |
| taken[count] = value; | |
| count++; | |
| } | |
| return taken; | |
| } | |
| // Materialize 10 odd numbers in an array | |
| console.log(take(10, oddNumbers())); | |
| // Output should be: | |
| // [1,3,5,7,9,11,13,15,17,19] |
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