以下代码片段中 for(;;) 的用途是什么?
What is the purpose of for(;;) in the following code snippet?
所以,我在 CodeGolf 上阅读了一些 Javascript 问题的答案,试图稍微提高我对 Javascript 的理解,并在以下问题 Generate Green Spraypaint Patterns Within the Answer I spotted a for loop that..[to me] is not the usual Syntax, & no matter how much I stare at it I can't figure out what this does. I can't find any referance to an operator ;;
on Mozilla's Javascript Operators 页面中注意到了这个答案&想知道是否有人可以解释下面代码中双分号的作用?
b.onclick = async function() {
b.disabled = true;
try {
await f(c, +s.value, +n.value, +m.value, JSON.parse(d.value));
} catch (ex) {
console.error(ex);
}
b.disabled = false;
}
async function f(canvas, size, number, moves, deltas) {
canvas.width = canvas.height = size;
let context = canvas.getContext('2d', { alpha: false });
context.fillRect(0, 0, size, size);
let image = context.getImageData(0, 0, size, size);
for (let i = 0; i < number; i++) {
let x = size / 2 | 0, y = x, j = moves;
for (;;) {
image.data[(x + y * size) * 4 + 1]++;
if (!j--) break;
let valid = deltas.map(([dx, dy]) => [x + dx, y + dy]).filter(([x, y]) => x >= 0 && y >= 0 && x < size && y < size);
if (!valid.length) break;
[x, y] = valid[valid.length * Math.random() | 0];
}
context.putImageData(image, 0, 0);
await new Promise(requestAnimationFrame);
}
}
<div>Size: <input id=s type=number min=1 value=250></div>
<div>Pixels: <input id=n type=number min=0 value=800></div>
<div>Moves: <input id=m type=number min=0 value=7000></div>
<div>Deltas: <input id=d value=[[1,2],[-1,2],[1,-2],[-1,-2],[2,1],[-2,1],[2,-1],[-2,-1]]></div>
<div><input id=b type=button value=Go!></div>
<canvas id=c>
可能真的很简单,但只是好奇学习。它只是一个占位符,用于从嵌套的 for 循环中获取完全相同的信息吗?
仅供其他人参考,这是开始或学习 Javascript none 以下工作.. lol
for(;;)
是一个 for
循环声明:
- 无初始化代码
- 无end-of-block表达
- 无终止条件
因此,它等同于 while(true)
- 它会一直循环直到遇到其中的 break
。
所以,我在 CodeGolf 上阅读了一些 Javascript 问题的答案,试图稍微提高我对 Javascript 的理解,并在以下问题 Generate Green Spraypaint Patterns Within the Answer I spotted a for loop that..[to me] is not the usual Syntax, & no matter how much I stare at it I can't figure out what this does. I can't find any referance to an operator ;;
on Mozilla's Javascript Operators 页面中注意到了这个答案&想知道是否有人可以解释下面代码中双分号的作用?
b.onclick = async function() {
b.disabled = true;
try {
await f(c, +s.value, +n.value, +m.value, JSON.parse(d.value));
} catch (ex) {
console.error(ex);
}
b.disabled = false;
}
async function f(canvas, size, number, moves, deltas) {
canvas.width = canvas.height = size;
let context = canvas.getContext('2d', { alpha: false });
context.fillRect(0, 0, size, size);
let image = context.getImageData(0, 0, size, size);
for (let i = 0; i < number; i++) {
let x = size / 2 | 0, y = x, j = moves;
for (;;) {
image.data[(x + y * size) * 4 + 1]++;
if (!j--) break;
let valid = deltas.map(([dx, dy]) => [x + dx, y + dy]).filter(([x, y]) => x >= 0 && y >= 0 && x < size && y < size);
if (!valid.length) break;
[x, y] = valid[valid.length * Math.random() | 0];
}
context.putImageData(image, 0, 0);
await new Promise(requestAnimationFrame);
}
}
<div>Size: <input id=s type=number min=1 value=250></div>
<div>Pixels: <input id=n type=number min=0 value=800></div>
<div>Moves: <input id=m type=number min=0 value=7000></div>
<div>Deltas: <input id=d value=[[1,2],[-1,2],[1,-2],[-1,-2],[2,1],[-2,1],[2,-1],[-2,-1]]></div>
<div><input id=b type=button value=Go!></div>
<canvas id=c>
可能真的很简单,但只是好奇学习。它只是一个占位符,用于从嵌套的 for 循环中获取完全相同的信息吗?
仅供其他人参考,这是开始或学习 Javascript none 以下工作.. lol
for(;;)
是一个 for
循环声明:
- 无初始化代码
- 无end-of-block表达
- 无终止条件
因此,它等同于 while(true)
- 它会一直循环直到遇到其中的 break
。