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; } ?>javascript - How to use Promise.all() on array of promises which take parameters? - Stack Overflow

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    let locArr = [{ x: 0, y: 0 }, { x: 2, y: 4 }, { x: 6, y: 8 }];

// my asynchronous function that returns a promise
function findLoc(x, y) {
    return new Promise((resolve, reject) => {
        let a = setTimeout(() => {
            resolve({ x: x * x, y: y * y });
        }, 500);
    });
}

Promise.all([
    // my problem is below
    findLoc(locArr[0].x, locArr[0].y),
    findLoc(locArr[1].x, locArr[1].y),
    findLoc(locArr[2].x, locArr[2].y),
]).then(values => {
    // all values from all the promises
});

    How can I write the Promise.all() function to take parameters from an array of varying size?

    I want to pass arguments to the array of promises accepted in the .all() method of the Promise class. What is the best way to do that?

    let locArr = [{ x: 0, y: 0 }, { x: 2, y: 4 }, { x: 6, y: 8 }];

// my asynchronous function that returns a promise
function findLoc(x, y) {
    return new Promise((resolve, reject) => {
        let a = setTimeout(() => {
            resolve({ x: x * x, y: y * y });
        }, 500);
    });
}

Promise.all([
    // my problem is below
    findLoc(locArr[0].x, locArr[0].y),
    findLoc(locArr[1].x, locArr[1].y),
    findLoc(locArr[2].x, locArr[2].y),
]).then(values => {
    // all values from all the promises
});

    How can I write the Promise.all() function to take parameters from an array of varying size?

    I want to pass arguments to the array of promises accepted in the .all() method of the Promise class. What is the best way to do that?

    • javascript
    • node.js
    • es6-promise
    Share Improve this question edited Jan 14, 2019 at 8:46 user10041268 asked Apr 10, 2018 at 3:11 EmmanuelEmmanuel 10.9k1 gold badge35 silver badges39 bronze badges 6
    • 1 This code looks OK at a glance, what's the issue? – Andy Ray Commented Apr 10, 2018 at 3:15
    • 2 you should create array const x = locArr.map(a => findLoc(a.x, a.y)) and pass x inside Promise.all – indapublic Commented Apr 10, 2018 at 3:16
    • @andy I don't want to hardcode the array values that are passed into the promises – Emmanuel Commented Apr 10, 2018 at 3:16
    • @indapublic could you explain that a bit more? – Emmanuel Commented Apr 10, 2018 at 3:19
    • 1 @EmmanuelNK Try this Promise.all(locArr.map(a => findLoc(a.x, a.y))).then(values => { console.log(values); }); – indapublic Commented Apr 10, 2018 at 3:21
     |  Show 1 more ment

    4 Answers 4

    Reset to default 10

    use map instead

    let locArr = [{
  x: 0,
  y: 0
}, {
  x: 2,
  y: 4
}, {
  x: 6,
  y: 8
}];

// my asynchronous function that returns a promise
function findLoc(x, y) {
  return new Promise((resolve, reject) => {
    let a = setTimeout(() => {
      resolve({
        x: x * x,
        y: y * y
      });
    }, 500);
  });
}

Promise.all(
  locArr.map(o => findLoc(o.x, o.y))
).then(values => {
  // all values from all the promises
  console.log(values)
});

    You can use map:

    let locArr = [{ x: 0, y: 0 }, { x: 2, y: 4 }, { x: 6, y: 8 }];

// my asynchronous function that returns a promise
function findLoc(x, y) {
    return new Promise((resolve, reject) => {
        let a = setTimeout(() => {
            resolve({ x: x * x, y: y * y });
        }, 500);
    });
}

Promise.all(
  locArr.map(//map location to promise
    location=>findLoc(location.x,location.y)
  )
).then(values => {
    // all values from all the promises
});

    This is a trick that requires to modify a little the input of findLoc:

    let locArr = [{ x: 0, y: 0 }, { x: 2, y: 4 }, { x: 6, y: 8 }];

// my asynchronous function that returns a promise
// 
function findLoc({x, y}) {
    return new Promise((resolve, reject) => {
        let a = setTimeout(() => {
            resolve({ x: x * x, y: y * y });
        }, 500);
    });
}

Promise.all(locArr.map(findLoc)).then(values => {
    console.log(values);
});

    Use map, like others said, but also adjust the findLoc() function for the simplest reading:

    let locArr = [{ x: 0, y: 0 }, { x: 2, y: 4 }, { x: 6, y: 8 }];

// my asynchronous function that returns a promise
function findLoc(coordinates) {
    return new Promise((resolve, reject) => {
        let a = setTimeout(() => {
            resolve({ 
              x: coordinates.x * coordinates.x, 
              y: coordinates.y * coordinates.y 
            });
        }, 500);
    });
}

Promise
    .all(locArr.map(findLoc))
    .then(values => {
        console.log(JSON.stringify(values, false, 2));
    });

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