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source.html
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<html>
<head>
<title>Polygon Data Processing</title>
<meta charset='utf-8'>
</head>
<body>
<script>
// Separate
const xcoords = [100,300,300,100];
const ycoords = [100,100,300,300];
let points;
// Listing 2 as a function
function test(approach, points) {
console.log(approach);
console.log('for(;;)');
for (let i=0; i<points.length; i++) // traditional loop
console.log(points[i]);
console.log('for..of');
for (let p of points) // for..of loop
console.log(p);
console.log('spread operator');
console.log(...points); // spread operator
console.log('JSON.stringify');
console.log(JSON.stringify(points));
}
// Listing 3
function iterator(xarr, yarr) {
let index = 0;
return {
next() {
return index < xarr.length
? { value: { x:xarr[index], y:yarr[index++] }, done: false }
: { done: !(index = 0) }; // reset state ...
},
[Symbol.iterator]() { return this; }
}
}
points = iterator(xcoords,ycoords);
console.log('Iterator - Listing 3');
console.log('for(;;)');
for (let i=0; i<points.length; i++) // traditional loop
console.log(points[i]);
console.log('for..of');
for (let p of points) // for..of loop
console.log(p);
console.log('spread operator');
console.log(...points); // spread operator
console.log('JSON.stringify');
console.log(JSON.stringify(points));
// Listing 4
function* generator(xarr, yarr) {
for (let i=0; i<xarr.length; i++)
yield {x: xarr[i], y: yarr[i]};
}
points = generator(xcoords,ycoords); // no way to reset
console.log('Generator - Listing 4');
console.log('for(;;)');
for (let i=0; i<points.length; i++) // traditional loop
console.log(points[i]);
console.log('for..of');
for (let p of points) // for..of loop
console.log(p);
points = generator(xcoords,ycoords); // no way to reset
console.log('spread operator');
console.log(...points); // spread operator
points = generator(xcoords,ycoords); // no way to reset
console.log('JSON.stringify');
console.log(JSON.stringify(points));
// Listing 5
const proxy = function(xarr, yarr) {
return new Proxy([], {
get: (points, key) => {
if (!isNaN(+key))
return {x:xarr[+key],y:yarr[+key]}
else
return xarr[key];
}
});
}
points = proxy(xcoords,ycoords);
console.log('Proxy - Listing 5');
console.log('for(;;)');
for (let i=0; i<points.length; i++) // traditional loop
console.log(points[i]);
console.log('for..of ... TypeError');
//for (let p of points) // for..of loop TypeError !
// console.log(p);
console.log('spread operator ... TypeError');
//console.log(...points); // spread operator
console.log('JSON.stringify');
console.log(JSON.stringify(points));
// Listing 6
const proxyEnhanced = function(xarr, yarr) {
const points = new Array(~~xarr.length);
points[Symbol.iterator] = function() {
let index = 0;
return {
next() {
return index < xarr.length
? { value: { x:xarr[index], y:yarr[index++] },
done: false }
: { done: true };
}
}
}
return new Proxy(points, {
get: (pts, key) => {
if (key === Symbol.iterator)
return points[Symbol.iterator].bind(points);
else if (!isNaN(+key))
return {x:xarr[key],y:yarr[key]};
else
return xarr[key];
}
});
}
points = proxyEnhanced(xcoords,ycoords);
console.log('Proxy Enhanced - Listing 6');
console.log('for(;;)');
for (let i=0; i<points.length; i++) // traditional loop
console.log(points[i]);
console.log('for..of ');
for (let p of points) // for..of loop
console.log(p);
console.log('spread operator');
console.log(...points); // spread operator
console.log('JSON.stringify');
console.log(JSON.stringify(points));
</script>
</body>
</html>