What is the simplest way to generate Fibonacci numbers in JavaScript?

Using a generator function allows you to yield each Fibonacci number on demand without precomputing the full sequence.

How does the generator maintain state between calls?

The generator keeps local variables for the last two numbers, updating them on each yield to produce the next Fibonacci number correctly.

Can I handle callCount larger than 50?

While the generator itself supports larger values, the problem constraints limit callCount to 50 to ensure predictable performance in interviews.

Why use a generator instead of a simple loop?

Generators implement the generate Fibonacci sequence core interview pattern by lazily yielding values, which is preferred in interviews for stateful iteration.

How do I retrieve the first N Fibonacci numbers using fibGenerator?

Initialize the generator, then call next() repeatedly N times, collecting each value into an array to produce the required sequence.

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Easy

auto_awesomeGenerate Fibonacci Sequence core interview pattern

LeetCode 题解工作台

生成斐波那契数列

请你编写一个生成器函数，并返回一个可以生成斐波那契数列的生成器对象。斐波那契数列的递推公式为 X n = X n-1 + X n-2 。这个数列的前几个数字是 0, 1, 1, 2, 3, 5, 8, 13 。示例 1：输入： callCount = 5 输出： [0,1,1,2,3]…

题目描述

请你编写一个生成器函数，并返回一个可以生成 斐波那契数列 的生成器对象。

斐波那契数列 的递推公式为 X_n = X_n-1 + X_n-2 。

这个数列的前几个数字是 0, 1, 1, 2, 3, 5, 8, 13 。

示例 1：

输入：callCount = 5
输出：[0,1,1,2,3]
解释：
const gen = fibGenerator();
gen.next().value; // 0
gen.next().value; // 1
gen.next().value; // 1
gen.next().value; // 2
gen.next().value; // 3

示例 2：

输入：callCount = 0
输出：[]
解释：gen.next() 永远不会被调用，所以什么也不会输出

提示：

0 <= callCount <= 50

lightbulb

解题思路

方法一

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function* fibGenerator(): Generator<number, any, number> {
    let a = 0;
    let b = 1;
    while (true) {
        yield a;
        [a, b] = [b, a + b];
    }
}

/**
 * const gen = fibGenerator();
 * gen.next().value; // 0
 * gen.next().value; // 1
 */

speed

复杂度分析

指标	值
时间	complexity is O(N) because each Fibonacci number up to callCount is generated once. Space complexity is O(N) for storing the resulting array, while the generator itself maintains constant extra memory for the last two numbers.
空间	O(N)

psychology

面试官常问的追问

外企场景

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Check if the candidate correctly uses JavaScript generator syntax for lazy evaluation.
question_mark
Notice if the candidate handles callCount = 0 without producing any output.
question_mark
Look for proper state management to yield each Fibonacci number sequentially without precomputing the entire sequence.

warning

常见陷阱

外企场景

error
Returning an array instead of a generator breaks the lazy generation pattern.
error
Incorrectly updating the previous two numbers can produce the wrong Fibonacci sequence.
error
Not handling callCount = 0 or edge values up to 50 can cause errors or extra iterations.

swap_horiz

进阶变体

外企场景

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Generate Fibonacci sequence recursively using a generator function.
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Yield only even Fibonacci numbers up to callCount.
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Implement a generator that supports negative Fibonacci indices as well.

help

常见问题

外企场景

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继续模式

Generate Fibonacci Sequence core interview pattern

用同一解题框架扩展到更多题目。

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同难度题单

简单

按当前难度继续强化稳定输出。

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