2021-10-15
1630
#vanilla javascript
Ibadehin Mojeed
72024
Oct 15, 2021 ⋅ 5 min read

Using JavaScript’s .at() method

Ibadehin Mojeed I'm an advocate of project-based learning. I also write technical content around web development.

Recent posts:

Why Kimi K2 is a frontend game-changer

Agentic AI for 5x less: Why Kimi K2 is a frontend game-changer

Kimi K2 doesn’t just tell you what to write or how to solve a problem; it writes the code, executes the tasks, and gets stuff done.

Chizaram Ken
Aug 22, 2025 ⋅ 8 min read
Gemini CLI vs Codex CLI: A Comparative Analysis

Does Gemini CLI fall short? Here’s how Codex compares

Compare Codex CLI vs Gemini CLI for real-world coding tasks. See strengths, weaknesses, and which AI CLI fits your developer workflow best.

Emmanuel John
Aug 20, 2025 ⋅ 8 min read
Is Next.js Still Developer-Friendly?

Is Next.js still developer-friendly?

The question isn’t whether Next.js is good or bad; it’s whether the productivity gains are worth the complexity tax.

Chizaram Ken
Aug 20, 2025 ⋅ 5 min read
Don’t Let AI Erase The Next Generation Of Dev Leaders

Don’t let AI erase the next generation of dev leaders

As AI tools take over more routine coding work, some companies are cutting early-career dev roles — a short-sighted move that could quietly erode the next generation of tech leaders if we aren’t careful.

Jack Herrington
Aug 19, 2025 ⋅ 6 min read
View all posts

6 Replies to "Using JavaScript’s <code>.at()</code> method"

  1. .at() is really useful but would be better to just add support into index operator. I know that there is possibility of having “-1” key/index, but what could have been done is if the key exist then return the value of the key else return value from length minus the supplied negative value. There is very rare possibility that “-1” is used as a key by anyone till date.

    1. I hope you understand its just not “-1” and can be “-2”, “-3”, …., “-100000000”,… you got me I think!

  2. I think your random number example has an issue. Math.random() returns between 0 and 1 inclusive which could put the index beyond the length of the array and result in an undefined.

    1. Hi James, thanks for reading. Be aware that Math.random() returns value between 0 (inclusive) and 1 (exclusive). Meaning it never returns 1. So by multiplying that with the array length of 3, we will never get a value of 3. So the output is 0, 1 and 2. And that will never result in an undefined. Thank you.

  3. Brilliant article thank you. I particularly liked your examples, and I had no idea you could store a value at the index -1!

    What’s really interesting is that if you set an array with a value at -1 such:

    “`
    let arr = [0, 1, 2];
    arr[-1] = -1
    “`

    And then use at:

    “`
    arr.at(-1) // returns 2
    “`

    It returns 2 rather than the value you set.

    Also, the fact that you can use decimal values with `at` is a gamechanger!

Leave a Reply