te')); return $arr; } /* 遍历用户所有主题 * @param $uid 用户ID * @param int $page 页数 * @param int $pagesize 每页记录条数 * @param bool $desc 排序方式 TRUE降序 FALSE升序 * @param string $key 返回的数组用那一列的值作为 key * @param array $col 查询哪些列 */ function thread_tid_find_by_uid($uid, $page = 1, $pagesize = 1000, $desc = TRUE, $key = 'tid', $col = array()) { if (empty($uid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('uid' => $uid), array('tid' => $orderby), $page, $pagesize, $key, $col); return $arr; } // 遍历栏目下tid 支持数组 $fid = array(1,2,3) function thread_tid_find_by_fid($fid, $page = 1, $pagesize = 1000, $desc = TRUE) { if (empty($fid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('fid' => $fid), array('tid' => $orderby), $page, $pagesize, 'tid', array('tid', 'verify_date')); return $arr; } function thread_tid_delete($tid) { if (empty($tid)) return FALSE; $r = thread_tid__delete(array('tid' => $tid)); return $r; } function thread_tid_count() { $n = thread_tid__count(); return $n; } // 统计用户主题数 大数量下严谨使用非主键统计 function thread_uid_count($uid) { $n = thread_tid__count(array('uid' => $uid)); return $n; } // 统计栏目主题数 大数量下严谨使用非主键统计 function thread_fid_count($fid) { $n = thread_tid__count(array('fid' => $fid)); return $n; } ?>What does x++ in JavaScript do? - Stack Overflow

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    What does x++ in JavaScript do? - Stack Overflow

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    I have a very short question, but it really confused me.

    var y = 3, x = y++;

    What is the value of x?

    I thought the answer should be 4, but actually it's 3.

    Can anyone explain me the reason?

    I have a very short question, but it really confused me.

    var y = 3, x = y++;

    What is the value of x?

    I thought the answer should be 4, but actually it's 3.

    Can anyone explain me the reason?

    • javascript
    Share Improve this question edited Sep 25, 2014 at 5:44 Barmar 782k56 gold badges546 silver badges660 bronze badges asked Sep 25, 2014 at 5:42 Yunhan LiYunhan Li 1531 gold badge3 silver badges8 bronze badges 2
    • 1 x = y++ here the value is assigned and then incremented. this x=++y will increment and assign. – Prabhu Murthy Commented Sep 25, 2014 at 5:44
    • when you do x = y++ ; first it will assign the value of y to x and then it increments. – K.D Commented Sep 25, 2014 at 5:45
    Add a ment  | 

    4 Answers 4

    Reset to default 11

    y++ is called post-increment -- it increments the variable after it returns the original value as the value of the expression. So 

    x = y++;

    is equivalent to:

    temp = y;
y = y + 1;
x = temp;

    If you want to return the new value, you should use ++y. This is called pre-increment because it increments the variable before returning it. The statement

    x = ++y;

    is equivalent to:

    y = y + 1;
x = y;

    In y++, ++ is called "post-increment operator". It first uses the value of y, then increments y. In this, is contrasts to a "pre-increment operator", ++y, which first increments y, then returns the incremented value.

    The ++ operator does two things. It increments a variable and it returns the value of the variable.

    If you prefix it, ie ++y, it will return the value after the increment (in your case, 4). If you postfix (y++)it, it will return the value before the increment (in your case 3. Note that the value of y is now still 4, but x was assigned before y was incremented). 

    var y = 3;
x = ++y;
console.log(x);

    This will result in 4

    This is called "pre-increment". Where it returns the incremented value .

    y++ is post-increment, which returns the original value.

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