如何在对象文字分配中指定动态值？

Question

This is what I got after running my code through JSLint:

Expected ':' and instead saw '+'. '"Book":"'+bookname+'"' line 3 column 23

Unexpected trailing space. '"Book":"'+bookname+'"'

I want to specify in a JSON string to find results if they contain the value of "bookid" in the "Book" column (cf. lines 1-4 below).

I understand that there are errors with the syntax. It was working great until I decided I needed to use a value from local storage. I am unsure of how to properly call a regular variable in this kind of query. What is wrong?

var bookname = localStorage.getItem('bookid');

var whereObject = {
    "$and": [{
        '"Book":"'+bookname + '"'
    }
    }, {
        "$or": [{
            "calf_id": {
                "$regex": "^" + value,
                "$options": "i"
            }
        }, {
            "cow_id": {
                "$regex": "^" + value,
                "$options": "i"
            }
        }, {
            "Sire": {
                "$regex": "^" + value,
                "$options": "i"
            }
        }, {
            "Color": {
                "$regex": "^" + value,
                "$options": "i"
            }
        }]
    }]
    };

return JSON.stringify(whereObject);

value is the value that is in the search bar.

I tried to change it using the advice given me, but then it just produces more warnings, similar to the ones I already have.

I basically need to know what the proper way to use a previously defined variable in a query. I don't know the proper syntax and haven't been able to find anything only

Answer 1

'"Book":"'+bookname + '"'

why are you using ' 's? i'm not sure why you are doing that.
in json, you should end the string before the : charachter. and after the : you type the value for the Book .

"KEY":"VALUE"

if value of Book is a string:

"Book" : "hello this is string"

if the value of Book is a variable:

"Book": bookname

if you want your Book to have a value of the bookname variable but enclosed in quotes, you do

"Book": "'" + bookname + "'"

if you look carefully and count the number of { and }'s in your json you see the number is not even! which means you have a mistake matching those. here is the valid json without syntax error:

{
  "$and": [


       {
         "Book":"bookname"
       },


       {
         "$or": [
             {"calf_id": {"$regex":"^" + value,"$options": "i"}},
             {"cow_id":  {"$regex":"^" + value,"$options": "i"}},
             {"Sire":    {"$regex":"^" + value,"$options": "i"}},
             {"Color":   {"$regex":"^" + value,"$options": "i"}}
         ]
       }


  ]
}