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; } ?>reactjs - How to pass optional parameter to a function in react and javascript? - Stack Overflow

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    i want to set an optional parameter to a function using javascript. i have a function defined like below,

    const function1 = () => {
    setValue(!open);
};

    i call it like below in other function

    const main_function = () => {
    function1();
}

    now i want to pass an optional parameter to function1 to accept an optional parameter that sets it to true or false instead of toggling based on previous value.

    how can i fix this. could someone help me with this thanks.

    i want to set an optional parameter to a function using javascript. i have a function defined like below,

    const function1 = () => {
    setValue(!open);
};

    i call it like below in other function

    const main_function = () => {
    function1();
}

    now i want to pass an optional parameter to function1 to accept an optional parameter that sets it to true or false instead of toggling based on previous value.

    how can i fix this. could someone help me with this thanks.

    • javascript
    • reactjs
    Share Improve this question asked Jul 17, 2020 at 13:24 sarithasaritha 6592 gold badges12 silver badges31 bronze badges 5
    • 3 function1 = (optionalParam = false) => {} – VLAZ Commented Jul 17, 2020 at 13:25
    • 3 setValue(!open); don't do this. Use functional update as your new state depends on the previous state. setValue(prevState => !prevState). – Ramesh Reddy Commented Jul 17, 2020 at 13:26
    • @VLAZ: so how do i call function1. – saritha Commented Jul 17, 2020 at 13:28
    • 3 Does this answer your question? Set a default parameter value for a JavaScript function – cbr Commented Jul 17, 2020 at 13:28
    • function1() or function1(true) or function1(false) – VLAZ Commented Jul 17, 2020 at 13:28
    Add a ment  | 

    5 Answers 5

    Reset to default 6

    I hope this helps someone, you can just set the value to null like code below:

     const function1 = ({arg1=null, arg2= false, arg3, ...}) => {
  
 }

    Pass a default value like so:

    function multiply(a, b = 1) {
  return a * b
}

multiply(5, 2)          // 10
multiply(5)             // 5

    Example taken from MDN docs

    we can't make function arguments optional in javascript directly. However, we can assign them a default value, in case no arguments is passed through. this is how you do it-

    const abc = (arg1, arg2= 'default value') => {
//arg1 is required. however if arg2 is not passed in any case, the default value //will be used in place.
}

    You can check the if the argument is defined or not, like:

    const function1 = (arg) => {
  setValue(arg === undefined ? !open : arg);
};

    As far as I can understand you want something like this.

    const function1 = (param) => {
    setValue(params ? true : false);
}

    It will set true if param is available otherwise false. Correct me if I'm wrong.

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