本文介绍了对于 let,如果数组中有相同的项目,则不递增的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试使用 find $in 数组增加 mongodb 中的一个项目,但是当数组中有相同的项目时,例如 ['apple','apple']
它应该增加两次但就我而言,它只增加一次,看看我的代码:
I'm trying to increment an item in my mongodb using find $in array, but when there is a same item in an array for example ['apple','apple']
it should increment twice but for my case, it only increment once, look at my code:
var newValue = 1;
var newSerialcode = req.body.serialCode;
var newBloodgroup = req.body.blood_group;
var newGetbloodcomponent = req.body.blood_component;
Bloodinventory.find({ blood_component : { $in : newGetbloodcomponent} ,blood_group: { $in :newBloodgroup},chapter: { $in: [id] }}, function(err, bloodinventoryDocs) {
for(let bloodinventory of bloodinventoryDocs) {
bloodinventory.num_stock = bloodinventory.num_stock + newValue ;
bloodinventory.save(function(err) {
if (err) {
console.log(err);
} else {
console.log('success');
}
});
}
});
推荐答案
我知道这已经有一段时间了,但这可能仍然对您(或其他人)有帮助,所以...
I know this has been a while, but this might still help you (or maybe someone else), so...
也许你可以试试这个:
var newValue = 1;
var newSerialcode = req.body.serialCode;
var newBloodgroup = req.body.blood_group;
var newGetbloodcomponent = req.body.blood_component;
Bloodinventory.find({ blood_component : { $in : newGetbloodcomponent} ,blood_group: { $in :newBloodgroup},chapter: { $in: [id] }}, function(err, bloodinventoryDocs) {
for(let bloodinventory of bloodinventoryDocs) {
// === change starts here === //
// filter into a new array all the places where this particular blood component occurs
let all_occurences = newGetbloodcomponent.filter(function(b){
return b === bloodinventory.blood_component;
});
// to avoid incurring unnecessary processing and/or database costs, only continue if an occurence was actually found
if(all_occurences.length > 0){
// increment it by that amount (which will be the number of items filtered into the array)
bloodinventory.num_stock = bloodinventory.num_stock + all_occurences.length;
// ^^ you could also write this as 'bloodinventory.num_stock += all_occurences.length;'
bloodinventory.save(function(err) {
if (err) {
console.log(err);
} else {
console.log('success');
}
});
};
// === change ends here === //
}
});
这篇关于对于 let,如果数组中有相同的项目,则不递增的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!