javascript 如何使用jQuery在for循环的迭代中不断添加到变量？
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How to continuously add to a variable on iteration of a for-loop, with jQuery?
提问by David says reinstate Monica
I'm trying to increase a number on each iteration of a forloop, in jQuery (1.4.2), by the width of the previous element.
我试图for在 jQuery (1.4.2) 中通过前一个元素的宽度在循环的每次迭代中增加一个数字。
I've tried the following:
我尝试了以下方法：
var
$lis = $('#bookmarks > li'),
liHeight = parseInt($lis.height()),
numLis = $lis.length;
console.log(numLis);
var totalLeft = '0';
console.log(totalLeft);
for (i=1; i<numLis; i++) {
var leftOffset = $lis.eq(i-1).width();
var leftTotal = leftOffset + leftTotal;
console.log(leftOffset +"/"+ leftTotal);
}
The output from this section is:
本节的输出是：
11 (the length of the array)
0 (the initial value of 'totalLeft')
97/97
117/214
90/
115/NaN
101/NaN
138/NaN
93/NaN
96/NaN
102/NaN
80/NaN
I've tried using parseInt()around one, and both, variables in the var leftTotal = leftOffset + leftTotal;variable assignment, to no avail. I've also tried using jQuery's each(), with the exact same result. Which is unsurprising, since I assigned the values in almost exactly the same way...
我试过parseInt()在var leftTotal = leftOffset + leftTotal;变量赋值中使用一个和两个变量，但无济于事。我也试过使用 jQuery's each()，结果完全相同。这并不奇怪，因为我以几乎完全相同的方式分配值......
There are two questions here:
这里有两个问题：
- Why is
leftTotalnot-a-number (NaN)? - How can I add the newvalue of
leftOffsetto the previous-iteration's value ofleftOffset?
- 为什么
leftTotal不是数字 (NaN)？ - 如何将 的新值添加
leftOffset到前一次迭代的 值leftOffset？
The console log shouldread something like:
控制台日志应该是这样的：
11
0
97/97
117/214
90/304
115/419
101/520
138/658
93/751
96/847
102/949
80/1029
Edited针对@KennyTM 进行了编辑：
Console.log output is now (more promising):
Console.log 输出现在是（更有希望）：
11
0
97 "/" "970"
117 "/" "117970"
90 "/" "90117970"
115 "/" "11590117970"
101 "/" "10111590117970"
138 "/" "13810111590117970"
93 "/" "9313810111590117970"
96 "/" "969313810111590117970"
102 "/" "102969313810111590117970"
80 "/" "80102969313810111590117970"
With regards to @Tomalak: yeah, it was a typo. Sadly it was a typo in both my code here and in the real darn script. ...sigh... Thanks for the catch, though, that seems to have done a lot to help out.
关于@Tomalak：是的，这是一个错字。遗憾的是，我在这里的代码和真正的该死的脚本中都有一个错字。......叹气......不过，感谢您的捕获，这似乎已经做了很多帮助。
...how embarrassing. =)
...多么尴尬。=)
采纳答案by Tomalak
It appears that you are not assigning to totalLeftin your code.
看来您没有totalLeft在代码中分配给。
Also, I think your code is wayto complicated and has subtle errors. Here is a more compact and jQuery-style version.
另外，我觉得你的代码是这样复杂的，有细微的错误。这是一个更紧凑和 jQuery 风格的版本。
var totalLeft = 0;
$('#bookmarks > li:gt(0)').prev().each(function () {
totalLeft += $(this).width();
});
At least, this generates the same number as the code in your own answer.
至少，这会生成与您自己的答案中的代码相同的数字。
回答by someGuy
i'd try somethin like this:
我会尝试这样的事情：
var leftTotal = 0
$('#bookmarks > li').each( function(){
leftTotal += parseInt(this.width()); // just to be sure its an int :)
console.log(this.width(); +"/"+ leftTotal);
});
回答by Roman
It seems you are not keeping the last value for the next iteration. i.e - put " var leftTotal" out of the loop, so it will keep the value for the next iteration and you'll add to it.
您似乎没有保留下一次迭代的最后一个值。即 - 将“var leftTotal”置于循环之外，因此它将保留下一次迭代的值，您将添加到它。
Hope I got you right :)
希望我说对了：）
回答by Praveen Prasad
var totalLeft = 0;
console.log(totalLeft);
for (i=1; i<numLis; i++) {
var leftOffset = $lis.eq(i-1).width();
var leftTotal = parseInt(leftOffset,10) + totalLeft;
console.log(leftOffset +"/"+ leftTotal);
}
回答by David says reinstate Monica
The solution was, apparently, to pay a little more attention to variable names, and use a parseInt:
显然，解决方案是多注意变量名称，并使用 parseInt：
var
$lis = $('#bookmarks > li'),
liHeight = parseInt($lis.height()),
numLis = $lis.length;
console.log(numLis);
var leftTotal = '0'; // somehow, between creating this var and the loop I started calling it something else 'totalLeft', for no known reason.
console.log(leftTotal);
for (i=1; i<numLis; i++) {
var leftOffset = $lis.eq(i-1).width();
var leftTotal = leftOffset + parseInt(leftTotal); // added the parseInt here to force it to be a number.
console.log(leftOffset, "/" , leftTotal);
}
Thanks to @Tomalak who caught my clinical blindness... =)
感谢@Tomalak 发现了我的临床失明... =)
