Mongodb将字符串解析为十进制/浮点数

Question

i'm new to mongoDB. I got my data as a string but i want to parse it to a decimal/ float . I found made this code but it doesn't seem to work. This is my code, it replaces - for 00, * for "", and parses it a float. It gives no errors, but the parseFloat(doc).toFixed(2) .

db.behuizingen.find().forEach(function(doc)
{
    var price = doc.Prijs.replace('€', ''); // it may be vary for your other document
    price = price.replace('-', '00');  
    price = price.replace('*', '');  
    doc.Prijs = Number(price);
    parseFloat(doc).toFixed(2)

    db.behuizingen.update({_id : doc._id} , doc;
})

Thanks in advance.

Answer 1

You did this wrong. Convert first and the Number() function of the shell has nothing to do with it. So replacing that line an continuing:

doc.Prijs = parseFloat(parseFloat(price).toFixed(2));
db.moederborden.update({_id : doc._id} , doc );

But also be beware. That usage of .update() where the second argument is there will "replace" the entire document with the contents of doc .

You may want to do this instead:

doc.Prijs = parseFloat(parseFloat(price).toFixed(2));
var update = { "$set": {} };

Object.keys(doc).each(function(key) {
    update["$set"][key] = doc[key];
});

db.moederborden.update({_id : doc._id} , update );

Which uses the $set operator, so that any existing values that were not referenced in your doc object are not overwritten when writing to the database.

Answer 2

I had a similar issue where we had not had decimal serialisation enabled correctly and so I wanted to update documents that were already in our database to use the Decimal type instead of String . I used the following script:

db.MyCollection.find({ Price: { $type: "string" } }).forEach(function(doc) { 
    print('Updating price for ' + doc._id);
    db.MyCollection.update( 
       { _id: doc._id },
       { $set : { Price: NumberDecimal(doc.Price) } }
    )
})

This only retrieves the documents that need updating by filtering on the field type, and then uses NumberDecimal to convert the string into a decimal.