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toString hack

  1. x=self+''
  2. console.log(
  3.   x[8],x[9],x[6],' ',
  4.   x[3],x[1],x[2],' ',
  5.   x[10],x[4],x[8],' ',
  6.   x[5],x[1],x[11]
  7. )

Hit the “Try it out” and open the console….

// hacks // javascript // strings

Smooth Bezier on Canvas

  1. const canvas = document.createElement('canvas');
  2. const c = canvas.getContext('2d');
  3.  
  4. document.body.appendChild(canvas);
  5.  
  6. function draw() {
  7.   canvas.width = window.innerWidth;
  8.   canvas.height = window.innerHeight;
  9.   c.fillStyle = 'gray';
  10.   c.fillRect(0, 0, canvas.width, canvas.height);
  11.  
  12.   c.strokeStyle = 'white';
  13.   c.lineWidth = 2;
  14.  
  15.   c.beginPath();
  16.   c.moveTo(0, 0);
  17.   bezierSkin([10, 10, 210, 10, 10, 300, 210, 300], false);
  18.   bezierSkin([200, 10, 330, 10, 250, 300]);
  19.   bezierSkin(
  20.     Array(30)
  21.       .fill(0)
  22.       .map((a, b) => (b % 2 == 0) * 300 + Math.random() * 300)
  23.   );
  24.   c.stroke();
  25. }
  26. window.addEventListener('resize', draw);
  27. draw();
  28.  
  29. // array of xy coords, closed boolean
  30. function bezierSkin(bez, closed = true) {
  31.   const avg = calcAvgs(bez);
  32.   const leng = bez.length;
  33.   let i, n;
  34.  
  35.   if (closed) {
  36.     c.moveTo(avg[0], avg[1]);
  37.     for (i = 2; i < leng; i += 2) {
  38.       n = i + 1;
  39.       c.quadraticCurveTo(bez[i], bez[n], avg[i], avg[n]);
  40.     }
  41.     c.quadraticCurveTo(bez[0], bez[1], avg[0], avg[1]);
  42.   } else {
  43.     c.moveTo(bez[0], bez[1]);
  44.     c.lineTo(avg[0], avg[1]);
  45.     for (i = 2; i < leng - 2; i += 2) {
  46.       n = i + 1;
  47.       c.quadraticCurveTo(bez[i], bez[n], avg[i], avg[n]);
  48.     }
  49.     c.lineTo(bez[leng - 2], bez[leng - 1]);
  50.   }
  51. }
  52.  
  53. // create anchor points by averaging the control points
  54. function calcAvgs(p) {
  55.   const avg = [];
  56.   const leng = p.length;
  57.   let prev;
  58.   for (var i = 2; i < leng; i++) {
  59.     prev = i - 2;
  60.     avg.push((p[prev] + p[i]) / 2);
  61.   }
  62.   // close
  63.   avg.push((p[0] + p[leng - 2]) / 2);
  64.   avg.push((p[1] + p[leng - 1]) / 2);
  65.   return avg;
  66. }

Being able to draw smooth lines that connect arbitrary points is something that I find myself needing very frequently. This is a port of an old old snippet of mine that does just that. By averaging control points of a quadratic bezier curve we ensure that our resulting Bezier curves are always smooth.

It would be very cool if html5 canvas implemented the Catmull Rom Spline but it unfortunately does not. The wonderful Raphael library used to have support for it.

// canvas // graphics // javascript // math // tricks

Obfuscated Canvas Commands

  1. const oCan = (
  2.   d = document,
  3.   b = d.body,
  4.   canvas = b.appendChild(document.createElement('canvas')),
  5.   c = canvas.getContext('2d'),
  6.   props = [],
  7.   o = {},
  8.   docs = {},
  9.   cmds = [],
  10.   L,
  11.   k,
  12.   du,
  13.   j,
  14.   draw,
  15.   id
  16. ) => {
  17.   ;(onresize = () => {
  18.     canvas.width = innerWidth
  19.     canvas.height = innerHeight
  20.     if (draw) {
  21.       clearTimeout(id)
  22.       id = setTimeout(() => cmds.forEach(v => draw(v)), 500)
  23.     }
  24.   })()
  25.  
  26.   Object.assign(b.style, { margin: 0, height: '100%' })
  27.  
  28.   // longer way: console.log(Object.getOwnPropertyNames(Object.getPrototypeOf(c)));
  29.   for (let i in c) props.push(i)
  30.  
  31.   // make alphabetical since object keys have
  32.   // no order
  33.   props.sort().map(i => {
  34.     L = i.match(/[A-Z]/)
  35.     k = i[0]
  36.     if (L) k += L[0]
  37.     du = 0
  38.     if (o[k]) {
  39.       j = 0
  40.       while (o[k]) k += i[++j]
  41.     }
  42.  
  43.     o[k] =
  44.       (typeof c[i])[0] == 'f'
  45.         ? (...args) => c[i].apply(c, args)
  46.         : v => (c[i] = v)
  47.     docs[i] = k
  48.   })
  49.  
  50.   console.log('docs:', JSON.stringify(docs, null, 2))
  51.  
  52.   return (draw = (s, cmd, currFn, args = [], part, fn, num) => {
  53.     cmd = s.split(/\s+/)
  54.     cmds.push(s)
  55.     c.save()
  56.     for (let i = 0; i < cmd.length; i++) {
  57.       part = cmd[i]
  58.       fn = o[part]
  59.       if (fn && currFn != fn) {
  60.         currFn && currFn.apply(c, args)
  61.         currFn = fn
  62.         args = []
  63.       } else {
  64.         num = parseFloat(part)
  65.         args.push(!isNaN(num) ? num : part)
  66.       }
  67.     }
  68.     currFn && currFn.apply(c, args)
  69.     c.restore()
  70.   })
  71. }
  72.  
  73. const c = oCan()
  74. // `font` & text not suppoted
  75. // make str a function so resize works?
  76. c(`
  77.   fS #ccc
  78.   fR 0 0 400 ${innerHeight}
  79.   fS blue
  80.   fR 40 0 20 20
  81.   gCl difference
  82.   ro .25
  83.   fR 50 0 30 30
  84.   gCl source-over
  85.   fS rgba(200,100,9)
  86.   fR 100 100 40 40
  87.   `)

I’ve had this idea for a long time, never bothered doing it until now. I wrote it in a semi-golfed style for no reason… Anyway, this lets you write canvas code in a strange obfuscated syntax that looks like this:

  1. c(`
  2.   fS #ccc
  3.   fR 0 0 400 ${innerHeight}
  4.   fS blue
  5.   fR 40 0 20 20
  6.   gCl difference
  7.   ro .25
  8.   fR 50 0 30 30
  9.   gCl source-over
  10.   fS rgba(200,100,9)
  11.   fR 100 100 40 40
  12.   `)

This snippet logs out some JSON that shows all the method aliases for the canvas context.

// canvas // codegolf // color // golfed // graphics // hacks // humor // javascript // json // strings // tricks

Proxy Quick DOM

  1. const spec = {
  2.   get(o, key) {
  3.     return o[key] != null ? 
  4.       o[key] : o[key] = (...args) => {
  5.         const el = document.createElement(key);
  6.         args.forEach(arg => { 
  7.           if (typeof arg === 'string') {
  8.             const span = document.createElement('span');
  9.             span.innerHTML = arg;
  10.             el.appendChild(span);
  11.           } else if (typeof arg === 'object') {
  12.             if (arg.tagName != null) {
  13.               el.appendChild(arg);
  14.             } else {
  15.               for (let i in arg) {
  16.                 el.setAttribute(i, arg[i]);
  17.               }
  18.             }
  19.           }
  20.         });
  21.         return el;
  22.       }
  23.   },
  24.   set(o, key, v) {
  25.     o[key] = v;
  26.   }
  27. }
  28.  
  29. const dom = new Proxy({}, spec);
  30.  
  31. document.body.appendChild(
  32.   dom.div(
  33.     dom.button('cool'), 
  34.     dom.h2('some text', { style: 'font-style: italic' }), 
  35.     dom.br(), 
  36.     dom.input({ placeholder: 'zevan' })
  37.   )
  38. );
  39.  
  40. const { div, input, label } = dom;
  41. document.body.appendChild(
  42.   div(
  43.     label(
  44.       'Slider:',
  45.       { 
  46.         for: 'slider', 
  47.         style: 'padding:1em;display:block' 
  48.       },
  49.       input({ id: 'slider', type: 'range' })
  50.     )
  51.   )
  52. );

In this snippet a proxy is used that makes all html node tagNames valid methods. Each method can take strings and HTMLElements as arguments in any order to create a dom structure. This may look familiar to people who have looked a bit deeper into the inner workings of some of the popular UI libraries of the last decade.

// dom // hacks // javascript // proxies // tricks // ui

Add Getter Setter to Object

  1. const target = {}
  2.  
  3. let value = null;
  4. Object.defineProperties(target, {
  5.   magic: {
  6.     get() {
  7.       console.log('- getter called::', value);
  8.       return value;
  9.     },
  10.     set(val) {
  11.       document.body.innerHTML += val + '<br>';
  12.       value = val;
  13.     }
  14.   }
  15. });
  16.  
  17. target.magic = 'xyz';
  18. target.magic = 'snippet';
  19. target.magic = 'zone';
  20. target.magic = '- last value';
  21.  
  22. console.log('getting', target.magic);

This snippet shows a way to add getters and setters to a specific key of an existing object. This is powerful for decorating configuration objects with special behaviors. This kind of thing can easily be created with a little more abstraction:

  1. const image = view({
  2.   tag: 'img', 
  3.   src: 'myImage.jpg',
  4.   x: '20%', 
  5.   y: '20%',
  6.   size: '50%'
  7. });
  8. const prev = view({
  9.   tag: 'button',
  10.   x: () => image.x,
  11.   y: () => image.bottom
  12. });
  13. const next = view({
  14.   tag: 'button',
  15.   x: () => image.right - this.width,
  16.   y: () => image.bottom
  17. });
// hacks // javascript // objects // tricks
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snippet.zone ~ 2021-24 /// {s/z}