[英]JavaScript for-loop question
Is it possible for a for-loop to repeat a number 3 times? for循环可以重复3次吗? For instance, 例如,
for (i=0;i<=5;i++)
creates this: 1,2,3,4,5. 创造了这个:1,2,3,4,5。 I want to create a loop that does this: 1,1,1,2,2,2,3,3,3,4,4,4,5,5,5 我想创建一个循环来执行此操作:1,1,1,2,2,2,3,3,3,4,4,4,5,5,5
Is that possible? 那可能吗?
for (i=1;i<=5;i++)
for(j = 1;j<=3;j++)
print i;
Yes, just wrap your loop in another one: 是的,只需将你的循环包装在另一个循环中:
for (i = 1; i <= 5; i++) {
for (lc = 0; lc < 3; lc++) {
print(i);
}
}
(Your original code says you want 1-5, but you start at 0. My example starts at 1) (您的原始代码表示您想要1-5,但是从0开始。我的示例从1开始)
You can have two variables in the for loop and increase i only when j is a multiple of 3: 你可以在for循环中有两个变量,只有当j是3的倍数时才增加i:
for (i=1, j=0; i <= 5; i = ++j % 3 != 0 ? i : i + 1) for(i = 1,j = 0; i <= 5; i = ++ j%3!= 0?i:i + 1)
Definitely. 当然。 You can nest for loops: 你可以嵌套for循环:
for (var i = 1; i < 6; ++i) {
for(var j = 0; j < 3; ++j) {
print(i);
}
}
Note that the code in your question will print 0, 1, 2, 3, 4, 5
, not 1, 2, 3, 4, 5
. 请注意,问题中的代码将打印0, 1, 2, 3, 4, 5
,而不是1, 2, 3, 4, 5
。 I have fixed that to match your description in my answer. 我已修复此问题以符合我在答案中的说明。
You could use a second variable if you really only wanted one loop, like: 如果你真的只想要一个循环,你可以使用第二个变量,如:
for(var i = 0, j = 0; i <= 5; i = Math.floor(++j / 3)) {
// whatever
}
Although, depending on the reason you want this, there's probably a better way. 虽然,根据你想要的原因,可能有更好的方法。
Just add a second loop nested in the first: 只需添加嵌套在第一个循环中的第二个循环:
for (i = 0; i <= 5; i++)
for (j = 0; j < 3; j++)
// do something with i
You can use nested for loops 您可以使用嵌套for循环
for (var i=0;i<5; i++) {
for (var j=0; j<3; j++) {
// output i here
}
}
You can use two variables in the loop: 您可以在循环中使用两个变量:
for (var i=1, j=0; i<6; j++, i+=j==3?1:0, j%=3) alert(i);
However, it's not so obvious by looking at the code what it does. 但是,通过查看代码它的作用并不是那么明显。 You might be better off simply nesting a loop inside another: 简单地将循环嵌套在另一个循环中可能会更好:
for (var i=1; i<6; i++) for (var j=0; j<3; j++) alert(i);
I see lots of answers with nested loops (obviously the nicest and most understandable solution), and then some answers with one loop and two variables, although surprisingly nobody proposed a single loop and a single variable. 我看到很多嵌套循环的答案(显然是最好和最容易理解的解决方案),然后是一个循环和两个变量的答案,尽管令人惊讶的是没有人提出单循环和单个变量。 So just for the exercise: 所以只是为了练习:
for(var i=0; i<5*3; ++i)
print( Math.floor(i/3)+1 );
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