taking from the start and end of an array in esnext

In esnext, you can use array destructuring to capture the first elements of an array, as well as the rest:

const [a, b, ...c] = [1, 2, 3, 4, 5]
console.log([a, b, c]) // [1, 2, [3, 4, 5]]

You can’t, however, put the rest operator at the start or in the middle of the destructuring expression. It must be at the end.

This is a bummer. CoffeeScript supports having a rest argument in the middle of a destructuring expression. Since esnext supports nested array destructuring, this limitation can at least be worked around concisely.

To implement getting the first two, the last two, and the middle, I can define a function leftrest which takes an array [l1, l2, l3..., r1, r2] and a number of rightmost arguments to expect, and returns an array with the first element containing the left arguments, followed by the rightmost arguments ([[l1, l2, l3...], r1, r2]):

const leftrest = (a, n) => {
  const rest = [...a]
  return [rest, ...rest.splice(-n)]
const [[a, b, ...c], d, e] = leftrest([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 2)
console.log([a, b, c, d, e])
// [ 1, 2, [ 3, 4, 5, 6, 7, 8 ], 9, 10 ]

The first line of the function const rest = [...a] simply copies the array before it’s handed to splice. Splice modifies an array in place, so it should be copied first. It’s best to use pure functions to avoid unintended side effects.

This isn’t DRY because it’s necessary to pass the number 2 to leftrest, but it’s close.

Finding Spanish words with Wikipedia and Wiktionary

There aren’t many language translation resources in open source, creative commons, or public domain. I was thinking about how I might start one and remembered that the English Wiktionary has many Spanish words. However, they are only linked in one direction, from the Spanish word to the English word.

How to find the Spanish word? One way is Spanish Wikipedia. For instance on the Instrumentos musicales por clasificación page, there are these words, which are on the English Wiktionary with the corresponding English words:

It seems like this could be used to bootstrap an open source translation dictionary.

fizzbuzz with psuedocode

Here’s a small experiment inspired by literate programming, future languages that aren’t plain text, and the occasional need for the same thing to be implemented in different languages. The idea is that code could can as an outline in a rich text editor and then be converted step by step into code. In the first step is psuedocode that reads well, at least to me, and at the end are working examples in JavaScript and Python.

Step 1

  • for each number n from 1 to 100, inclusive
    • let s be an empty string
    • if n is evenly divisible by 3, append “Fizz” to s
    • if n is evenly divisible by 5, append “Buzz” to s
    • if s is empty, print n
    • if s is not empty, print s

Step 2 (JavaScript)

  • for (let n=1; n <= 100; n++)
    • let s = ”
    • if (n % 3 == 0) s += ‘Fizz’
    • if (n % 5 == 0) s += ‘Buzz’
    • if (s == ”) console.log(n)
    • if (s != ”) console.log(s)

Step 2 (Python)

  • for n in range(1, 101)
    • s = ”
    • if n % 3 == 0
      • s += ‘Fizz’
    • if n % 5 == 0
      • s += ‘Buzz’
    • if s == ”
      • print(n)
    • if s != ”
      • print(s)

Step 3 (JavaScript)

for (let n = 1; n <= 100; n++) {
  let s = ''
  if (n % 3 == 0) s += 'Fizz'
  if (n % 5 == 0) s += 'Buzz'
  if (s == '') console.log(n)
  if (s != '') console.log(s)

Step 3 (Python)

for n in range(1, 101):
    s = ''
    if n % 3 == 0:
        s += 'Fizz'
    if n % 5 == 0:
        s += 'Buzz'
    if s == '':
    if s != '':

2018 New Year’s Resolutions

I’m setting three resolutions for the next year:

  1. Go for a 10 mile run each month
  2. Study Spanish for at least 10 hours each month
  3. Run my first triathlon

Each of these are things that I think are very achievable, and likely not to be achieved if I don’t resolve to do them. They also don’t take up so much time and effort that they prevent me from coming up with new goals during the year.


Perfectionism is stifling.

A perfectionist should look for good strategies to get work done despite their perfectionism.

Some strategies, such as trying to fake being a non-perfectionist, are not good ones.

Under this strategy, the perfectionist works against their advantages, while making a pathetic attempt at denying their true nature.

DigitalOcean FTW

In the past, DigitalOcean had a big security issue, and I told people that I don’t recommend using them. They responded to the issue pretty well, but I felt that the issue they had should not have happened in the first place.

Some time has passed since then without any major issues, and they hired an all-star systems administrator. Recently I was working on a project using AWS, and in my search for information, I came across some useful tutorial pages on their site. Because of this, when the time came to switch hosts for my personal site, I started using DigitalOcean and have had a great experience. I can heartily recommend them now.

Of course, they may still have major security issues, but I expect that they’ll have better than average security going forward.

jschain: angular directive and a test (#15)

I built a random-color angular directive with a test on the same page. I started by using plunkr but gave up and used Bower because my connection was unreliable. I learned that angular-mocks is a counterpart to Jasmine in that it exports global variables for convenience. Also, angular-mocks must be loaded after Jasmine. I learned this the hard way.