CODEWITHSUNDEEP
javascriptarraysjsonobjectecmascript-6
Eye Patch
Eye Patch

Reputation: 991

Difference between obj.key=value and obj.set(key, value)?

So while trying to update a document in mongoose, I realized that when I do obj.key=value to a document I obtained with Model.findOne(), it doesn'st assign the property to its value. But after trying obj.set(key, value), the property is assigned to its value in the document. So why is that? Usually when i do the first method to an object, the object gets the property. What is the .set() function? Does it have something to do with mongoose? 

//this works
async function updateItem(){
        let updatedItem = await Item.findOne({name:req.body.itemName});
        Object.entries(req.body).forEach(elem=>{
            if(elem[0]!=="itemName"){
                updatedItem.set(elem[0], elem[1]);
            };
        });
    };
    updateItem();
});


//this doesn't work
async function updateItem(){
        let updatedItem = await Item.findOne({name:req.body.itemName});
        Object.entries(req.body).forEach(elem=>{
            if(elem[0]!=="itemName"){
                updatedItem.elem[0] = elem[1];
            };
        });
    };
    updateItem();
});

Upvotes: 0

Views: 75

Answers (1)

Jack Bashford
Jack Bashford

Reputation: 44107

It means that updatedItem is not an object, it's a Map, and to add items to a Map you need to use the get method.

Another thing to point out is that when you set updatedItem.elem[0], you're literally trying to add the key "elem[0]" to updatedItem. To fix this, you need to use dynamic property notation with square brackets:

updatedItem[elem[0]] = elem[1];

This makes a new key with the value of elem[0], instead of the key being elem[0].

Upvotes: 1

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