nodejs json.parse保留科学计数法

Question

Can anyone help me figure out a JSON.parse() issue I'm facing? This is utilizing Node.js v6.9.

Basically, I need to store some data within my database EXACTLY as I see it in a file. While I have the vast majority of this working, there's a couple kinks I'm trying to iron out.

First issue is when I run across scientific notation within an array. When I parse this, it does NOT preserve "en" unless it's greater than 6. Thus, the result is that I get a non-scientific notation value stored in an array. Is there some way to force the parse() function to preserve this? See examples I ran from my debugger within Visual Studio Code:

JSON.parse('[3.908e-3, -5.775e-7]');
Array[2] [0.003908, -5.775e-7]

JSON.parse('[3.908e-4, -5.775e-7]');
Array[2] [0.0003908, -5.775e-7]

JSON.parse('[3.908e-5, -5.775e-7]');
Array[2] [0.00003908, -5.775e-7]

JSON.parse('[3.908e-6, -5.775e-7]');
Array[2] [0.000003908, -5.775e-7]

JSON.parse('[3.908e-7, -5.775e-7]');
Array[2] [3.908e-7, -5.775e-7]

Second issue is another formatting issue. JSON.parse doesn't seem to preserve the decimals. Like the first issue above, is it possible to make JSON.parse() preserve the number notation exactly as its given? Notice how the parse is chopping off the zero decimal.

JSON.parse('[1.0, 2.0]')
Array[2] [1, 2]

Was reading up on reviver functions that you can pass as a second argument to the parse() function, but I'm a bit lost on these. Do I need to write my own custom function to preserve the format as is?

Edit: More information provided: I'm trying to take a complex JSON object as-is, and store the entire structure in my Postgresql database. The file itself is initially uploaded as a Uint8Array. I then do a toString() on that, and do a JSON.parse on the result. So if this was the original contents of the uploaded file, I can do this:

uploadedFile.toString();
"{
    "someKey": {
      "id": "COG32",
      "control_id": "00D2FFFF0000",
      "coefficients": [3.908e-3, -5.775e-7]
    }
}"

Then I can do this:

JSON.parse(uploadedFile.toString());
{
    "someKey": {
      "id": "COG32",
      "control_id": "00D2FFFF0000",
      "coefficients": [3.00908, -5.775e-7]
    }
}

Some of the properties in the file I'm given contain arrays of two scientific notation values.

In order to do this, I'm parsing the json string to an object and able to iterate the keys and all its properties to store everything within its own record in the database. This all works great, except for the fact that JSON.parse is automatically transforming 3.908e-3 into 3.003908.
I also need to recreate this json object EXACTLY as it was given to me, from the database. I understand that they are the "same" numbers. But when it comes to diffing the files (the original json object and the one I re-create from the database...), they are very different. .toExponential() seems to give me the exponential variant of the number, but in string format. If I were to use that, I would wind up with:

["3.908e-3", "-5.775e-7"]

When what I want is:

[3.908e-3, -5.775e-7]

Answer 1

In your JSON, the data is stored as a type NUMBER; when you write 3.908e-4 it is equal to 0.0003908.

You then have 2 choices:

• store your data as a string so it keeps the format (which is ok if you do not want to perform calculations) JSON.parse('["3.908e-3", "-5.775e-7"]');
• force a format when you print the data eg (0.0004345).toExponential() --> 4.345e-4 or (1).toFixed(1) --> 1.0;