Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
A Pen by Vlad Bezden on CodePen.
| 'option strict'; | |
| function* fibonacci() { | |
| let prev = 0, | |
| curr = 1; | |
| while (true) { | |
| // this line will work, but it runs slower. Explicit assignment is much faster | |
| //[prev, curr] = [curr, prev + curr]; | |
| prev = curr; | |
| curr += prev | |
| yield curr; | |
| } | |
| } | |
| function runner(maxFibValue) { | |
| let acc = 0, | |
| value = 0; | |
| for (let value of fibonacci()) { | |
| if (value > maxFibValue) { | |
| break; | |
| } else if (value % 2 === 0) { | |
| acc += value; | |
| } | |
| } | |
| return acc; | |
| } | |
| startTime = performance.now(); | |
| const result = runner(4000000); | |
| const stopTime = performance.now(); | |
| console.log(`Result: ${result}. Execution time: ${(stopTime - startTime).toFixed(4)} ms`); |