Snippet Zone

Flatten Array Golf

```
 
```

console.log([100, 200, [2], [3, 4, [2, 3, [5]], 100]]+'')

```
// outputs: "100,200,2,3,4,2,3,5,100"
```

Coercing a multidimensional array to a string flattens it and joins it with commas

October 5, 2021

// arrays // codegolf // javascript // strings

ASCII Circles (Bresenham Fun)

```
// some circles made of text
```
```
 
```
```
const cols = 50;
```
```
const rows = 50;
```
```
const sym = '.';
```
```
const body = document.body;
```
```
 
```
```
Object.assign(body.style, {
```
```
  userSelect: 'none',
```
```
  fontFamily: 'Courier, monospace',
```
```
  position: 'fixed', 
```
```
  width: '100%',
```
```
  height: '100%',
```
```
  margin: 0
```
```
});
```
```
 
```
```
const el = body.appendChild(
```
```
  document.createElement('span')
```
```
);
```
```
el.innerHTML = sym;
```
```
 
```
```
Object.assign(el.style, {
```
```
  position: 'absolute',
```
```
  left: '50%',
```
```
  top: '50%',
```
```
  wordWrap: 'break-word',
```
```
  cursor: 'pointer'
```
```
});
```
```
 
```

const charSize = el.getBoundingClientRect().width;

```
const elWidth = charSize * cols;
```
```
el.style.display = 'block'
```
```
el.style.width = `${elWidth}px`;
```
```
 
```
```
const info = body.appendChild(
```
```
  document.createElement('div')
```
```
);
```
```
 
```
```
Object.assign(info.style, {
```
```
  background: '#fff',
```
```
  padding: '4px',
```
```
  position: 'absolute'
```
```
})
```

info.innerHTML = 'click/tap and hold for different fx';

```
 
```
```
function resize() {
```
```
  const scl = Math.min(
```
```
    1.23, 
```

    Math.min(innerWidth, innerHeight) / elWidth * .93

```
  );
```

  el.style.transform = `translate(-50%, -50%) scale(${scl}, ${scl * .55})`

```
}
```
```
addEventListener('resize', resize);
```
```
resize();
```
```
 
```
```
const size = cols * rows;
```
```
const pix = sym.repeat(size);
```
```
el.innerHTML = pix;
```
```
 
```
```
let cells = pix.split('')
```
```
const blank = cells.concat();
```
```
 
```
```
function setSym(x, y, col) {
```
```
  const idx = x + y * cols;
```
```
  if (cells[idx] != null) {
```
```
    cells[idx] = col;
```
```
  }
```
```
  return setSym
```
```
}
```
```
 
```
```
const grad = '::;|0UU888NN';
```
```
function circ(shooter) {
```

  let x = Math.round(Math.random() * cols);

  let y = Math.round(Math.random() * rows);

```
  const rad = Math.round(
```
```
    shooter ? Math.random() * 2 :
```

      Math.random() * Math.random() * 13 + 1

```
  );
```
```
 
```

  const sym = shooter ? '#' : grad.charAt(rad % grad.length);

```
  let speed = rad / 10 + .1;
```
```
  let dir = Math.random() * 2 - 1;
```
```
  return () => {
```

    drawCircle(x, y, rad, sym, shooter);

```
    y += speed;
```
```
    if (shooter) x += speed * 3 * dir;
```
```
    if (y > rows + 10) y = -14;
```
```
  }
```
```
}
```
```
 
```
```
const circs = [];
```
```
const NUM = 40;
```
```
for (let i = 0; i < NUM; i++) {
```
```
  circs.push(circ(Math.random() > 0.5))
```
```
}
```
```
 
```
```
let down;
```

document.addEventListener('mousedown', () => {

```
  down = true;
```
```
});
```

document.addEventListener('mouseup', () => {

```
  down = false;
```
```
});
```

document.addEventListener('touchstart', () => {

```
  down = true;
```
```
});
```

document.addEventListener('touchend', () => {

```
  down = false;
```
```
});
```
```
 
```
```
let tweak;
```
```
let tweakChoice;
```
```
let tweakChance = 0.4;
```

const clear = () => cells = blank.concat();

```
 
```
```
function draw() {
```
```
  if (!down) {
```
```
    tweak = false;
```
```
    tweakChoice = Math.random();
```
```
    clear();
```
```
  } else {
```
```
    if (tweakChoice < tweakChance) {
```
```
      tweak = true;
```
```
      clear();
```
```
    }
```
```
  }
```
```
 
```
```
  circs.forEach(circ => circ());
```
```
  el.innerHTML = cells.join('');
```
```
}
```
```
 
```

// 60fps is too fast, so use 30ms interval

```
setInterval(draw, 30);
```
```
 
```
```
function hLine(xp, yp, w, col) {
```
```
  for (let i = 0; i < w; i++) {
```
```
    setSym(xp + i, yp, col);
```
```
  }
```
```
  return hLine;
```
```
}
```
```
 
```
```
// bresenham circle
```

function drawCircle(xp, yp, radius, sym = '@', isFilled) {

```
  if (isFilled && tweak) sym = '';
```
```
 
```
```
  xp = parseInt(xp, 10);
```
```
  yp = parseInt(yp, 10);
```
```
  radius = parseInt(radius, 10);
```
```
  let balance = -radius,
```
```
    xoff = 0,
```
```
    yoff = radius;
```
```
 
```
```
  while (xoff <= yoff) {
```
```
    const p0 = xp - xoff;
```
```
    const p1 = xp + xoff;
```
```
 
```
```
    const p2 = yp + yoff;
```
```
    const p3 = yp - yoff;
```
```
    const p4 = yp + xoff;
```
```
    const p5 = xp + yoff;
```
```
    const p6 = xp - yoff;
```
```
    const p7 = yp - xoff;
```
```
 
```
```
    if (isFilled) {
```
```
      const w0 = xoff + xoff;
```
```
      const w1 = yoff + yoff;
```
```
 
```
```
      hLine
```
```
        (p0, yp + yoff, w0, sym)
```
```
        (p0, yp - yoff, w0, sym)
```
```
        (p6, yp + xoff, w1, sym)
```
```
        (p6, yp - xoff, w1, sym);
```
```
 
```
```
    } else {
```
```
      setSym
```
```
        (p1, p2, sym)
```
```
        (p0, p2, sym)
```
```
        (p0, p3, sym)
```
```
        (p1, p3, sym)
```
```
        (p5, p4, sym)
```
```
        (p6, p4, sym)
```
```
        (p6, p7, sym)
```
```
        (p5, p7, sym);
```
```
    }
```
```
 
```

    // never been able to find the original

```
    // source for the below condition 
```

    // more info here: https://actionsnippet.com/?p=492

    if ((balance += xoff++ + xoff) >= 0) {

```
      balance -= --yoff + yoff;
```
```
    }
```
```
  }
```
```
}
```

This is a bit of a longer snippet that uses the Bresenham circle drawing algorithm to draw some circles with text. I recommend looking at it with the fullscreen button.

I like to do this:

```
hLine
```
```
  (p0, yp + yoff, w0, sym)
```
```
  (p0, yp - yoff, w0, sym)
```
```
  (p6, yp + xoff, w1, sym)
```
```
  (p6, yp - xoff, w1, sym);
```

Make a function return itself, so that if you need to call it many times without having to repeat the function name. Because this isn’t a common style it is generally frowned upon, I’m always tempted to use it at work for some reason… maybe next April fools.

September 26, 2021

// animation // arrays // graphics // hacks // humor // javascript // math // random // strings // tricks

Cistercian Numerals (semi-golfed)

```
N = -1
```
```
S = 30
```
```
H = 90
```
```
h = 45
```
```
d = document
```
```
b = d.body
```
```
m = _ => d.createElement(_)
```
```
a = _ => b.appendChild(_)
```
```
 
```
```
with(a(
```
```
    Object.assign(
```
```
      m`canvas`,
```
```
      { width: 80, height: 120 }
```
```
    )
```
```
  ).getContext`2d`
```
```
) { 
```
```
  a(m`br`)
```
```
 
```
```
  L = (a, b, C, d) => {
```
```
    moveTo(a, b)
```
```
    lineTo(C, d)
```
```
  }
```
```
 
```
```
  M = _ => L(0, 0, 0, H)
```
```
  O = _ => L(0, 0, S, 0)
```
```
  W = _ => L(0, S, S, S)
```
```
  T = _ => L(0, 0, S, S)
```
```
  F = _ => L(0, S, S, 0)
```
```
  X = _ => L(S, 0, S, S)
```
```
 
```
```
  D = [
```
```
    _ => {},
```
```
    O, W, T, F, 
```
```
    [O,F],
```
```
    X,
```
```
    [O,X],
```
```
    [W,X],
```
```
    [O,W,X]
```
```
  ]
```
```
 
```
```
  n = s => {
```
```
    [...s].reverse().map((l, i) => {
```
```
      save()
```
```
      translate(S+9, h+9)
```
```
      scale(N**i, N**~~(i/2))
```
```
      translate(0, -h)
```

      M() ;[D[l]].flat().map(x => x && x())

```
      restore()
```
```
    })
```
```
  }
```
```
 
```
```
  a(m`input`).oninput = e => {
```
```
    clearRect(0, 0, 80, 120)
```
```
    beginPath()
```
```
    n(~~e.target.value+'')
```
```
    stroke()
```
```
  }
```
```
}
```

Type any number from 0-9999 into the input field and see the corresponding Cistercian Numeral. This snippet is partially golfed, I left the canvas commands intact to make things a bit easier to understand.

Simpler SVG Version

This one hardcodes all numbers 0-9 as paths, unlike the canvas version which only defines 1,2,3,4 and 6 as paths and then combines them to create 5,7,8 and 9.

```
h='innerHTML'
```
```
C='children'
```
```
 
```
```
document.body[h]=`
```

<svg id=G width=99 viewBox="0 0 80 120"

  style="stroke:black;fill:none;overflow:visible">

```
  <g transform="translate(30,2)">
```
```
    <path d="M0 0L 30 0"/>
```
```
    <path d="M0 30L 30 30"/>
```
```
    <path d="M0 0L 30 30"/>
```
```
    <path d="M0 30L30 0"/>
```
```
    <path d="M0 30L30 0 0 0"/>
```
```
    <path d="M30 0L30 30"/>
```
```
    <path d="M30 30L30 0 0 0"/>
```
```
    <path d="M0 30L30 30 30 0"/>
```
```
    <path d="M0 30L30 30 30 0 0 0"/>
```
```
  </g>
```

  <g transform=translate(30,2)scale(-1,1)></g>

  <g transform=translate(30,92)scale(1,-1)></g>

  <g transform=translate(30,92)scale(-1,-1)></g>

```
  <path id=m d="M 30 2 L 30 92"/>
```
```
</svg>
```

<style>path:not(#m){opacity:0}</style><br>

```
<input id=I>`
```
```
 
```
```
c=G[C]
```
```
p=c[0][h] 
```
```
 
```
```
n = s => 
```
```
  [...s].reverse().map((l, i) => 
```

   l-1>-1 && (c[i][C][l-1].style.opacity=1))

```
 
```
```
I.oninput = e => {
```
```
  for(i=0;i<4;i++)c[i][h]=p
```
```
  n(~~e.target.value+'')
```
```
}
```

September 24, 2021

// arrays // canvas // codegolf // graphics // hacks // javascript // math

Array Based Collision Cells

```
((
```
```
  d = document,
```
```
  b = d.body,
```
```
  canvas = b.appendChild(
```
```
    d.createElement('canvas')
```
```
  ),
```
```
  c = canvas.getContext('2d'),
```
```
  r = _ => Math.random(),
```
```
  map = [
```
```
    [0, 0, 0, 0, 0, 2],
```
```
    [1, 1, 0, 0, 0, 1],
```
```
    [1, 1, 2, 0, 0, 0],
```
```
    [2, 2, 0, 0, 0, 1],
```
```
    [0, 1, 0, 0, 2, 0],
```
```
    [2, 0, 0, 0, 2, 1],
```
```
  ],
```
```
  mapW = map[0].length,
```
```
  mapH = map.length,
```
```
  cols = [, 'red', 'black'],
```
```
  cell = (
```
```
    x, y, idx,
```
```
    col = cols[idx],
```
```
    size = 30,
```
```
    xp = x * size,
```
```
    yp = y * size,
```
```
    dir, 
```
```
    mv = f => {
```
```
      map[y][x] = 0
```
```
      f()
```
```
      map[y][x] = idx
```
```
    }
```
```
  ) => (move) => {
```
```
    if (move) {
```
```
      dir = ~~(r() * 4)
```
```
      if (dir == 0 &&
```
```
        x != 0 &&
```
```
        map[y][x - 1] == 0) {
```
```
        mv(_ => x--)
```
```
      } else if (dir == 1 &&
```
```
        x != mapW - 1 &&
```
```
        map[y][x + 1] == 0) {
```
```
        mv(_ => x++)
```
```
      } else if (dir == 2 &&
```
```
        y != 0 &&
```
```
        map[y - 1][x] == 0) {
```
```
        mv(_ => y--)
```
```
      } else if (dir == 3 &&
```
```
        y != mapH - 1 &&
```
```
        map[y + 1][x] == 0
```
```
      ) {
```
```
        mv(_ => y++)
```
```
      }
```
```
    }
```
```
 
```
```
    xp += (x * size - xp) / 4
```
```
    yp += (y * size - yp) / 4
```
```
    c.fillStyle = col
```
```
    c.fillRect(xp, yp, size, size)
```
```
    c.strokeStyle = 'gray'
```
```
    c.strokeRect(xp, yp, size, size)
```
```
  },
```
```
  cells = [],
```
```
  w, h, idx, val, i, j,
```
```
  draw = () => {
```
```
    c.fillStyle = 'gray'
```
```
    c.fillRect(0, 0, w, h)
```
```
 
```
```
    idx = ~~(r() * mapH * mapW)
```
```
 
```
```
    cells.forEach((cell, i) =>
```
```
      cell(idx == i && r() < .3))
```
```
  }
```
```
) => {
```
```
  b.style.margin = 0
```
```
 
```
```
  onresize = () => {
```
```
    w = canvas.width = innerWidth
```
```
    h = canvas.height = innerHeight
```
```
    draw()
```
```
  }
```
```
  onresize()
```
```
 
```
```
  for (i = 0; i < mapH; i++) {
```
```
    for (j = 0; j < mapW; j++) {
```
```
      val = map[i][j]
```

      if (val != 0) cells.push(cell(j, i, val))

```
    }
```
```
  }
```
```
 
```
```
  setInterval(draw, 16)
```
```
})()
```

Array based avoid. I was about to port an old thing that was similar to this and then thought it would be more fun to speedcode it instead. The result is a slightly golfed version of this old thing.

September 23, 2021

// animation // arrays // canvas // codegolf // graphics // javascript // math

Array.at Negative Indices

```
const arr = [
```
```
  'one', 'two', 
```
```
  'three', 'four'
```
```
];
```
```
console.log(
```
```
  arr.at(-1), 
```
```
  arr.at(-2), 
```
```
  arr.at(0)
```
```
);
```

Array.at allows negative index values to be used to read elements from an array. I’ve seen this done using a Proxy in the past.

September 22, 2021

// arrays // javascript

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