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I have a JSON file that contains numbers of type float. I would like to convert them to two decimal places before using the file in a react application. I understand that I need to use number.toFixed(2) to achieve that. How could I achieve that in the JSON file? A sample of the file:

[
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 3457.7132034355964,
    "value_avg_minus_stdv": 3415.2867965644036,
},
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 4457.7132034355964,
    "value_avg_minus_stdv": 3425.2867965644036,
}
]

The final result should be :

[
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 3457.71,
    "value_avg_minus_stdv": 3415.29,
},
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 4457.71,
    "value_avg_minus_stdv": 3425.29,
}
]

Thanks!

I have a JSON file that contains numbers of type float. I would like to convert them to two decimal places before using the file in a react application. I understand that I need to use number.toFixed(2) to achieve that. How could I achieve that in the JSON file? A sample of the file:

[
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 3457.7132034355964,
    "value_avg_minus_stdv": 3415.2867965644036,
},
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 4457.7132034355964,
    "value_avg_minus_stdv": 3425.2867965644036,
}
]

The final result should be :

[
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 3457.71,
    "value_avg_minus_stdv": 3415.29,
},
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 4457.71,
    "value_avg_minus_stdv": 3425.29,
}
]

Thanks!

• javascript
• reactjs

Share Improve this question Follow edited Jun 19, 2020 at 9:28 Lajos Arpad 77.3k4040 gold badges117117 silver badges221221 bronze badges asked Jun 19, 2020 at 9:22 Derrick OmanwaDerrick Omanwa 52511 gold badge1010 silver badges2727 bronze badges 3

• you would have to manually loop this array and apply toFixed on each property you desire to update – Sudhanshu Kumar Commented Jun 19, 2020 at 9:24
• btw, you have no JSON, because JSON is a string. do you want to get a JSON or parse it? – Nina Scholz Commented Jun 19, 2020 at 9:27
• 1 toFixed() will produce a string, not a number as in your example. To round the numbers to two fraction digits, use Math.round() with a factor like so: x = Math.round(x * 100) / 100. Note that the precision of floating point numbers may not exactly represent these numbers. – Lucero Commented Jun 19, 2020 at 9:30

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5 Answers 5

Sorted by: Reset to default 6

You could pass reviver function to the JSON.parse method to prescribes how the value originally produced by parsing is transformed, before being returned:

JSON.parse(jsonString, (key, value) =>
  typeof value === "number" ? Math.round(value * 100) / 100 : value
);

Replace Math.round(value * 100) / 100 with Math.round((value + Number.EPSILON) * 100) / 100 or +value.toFixed(2) or other methods as you wish.

More about JSON.parse

use toFixed

Like this

[
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 3457.7132034355964,
    "value_avg_minus_stdv": 3415.2867965644036,
},
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 4457.7132034355964,
    "value_avg_minus_stdv": 3425.2867965644036,
}
].map(x => ({
    ...x,
    value_avg_plus_stdv: +x.value_avg_plus_stdv.toFixed(2),
    value_avg_minus_stdv: +x.value_avg_minus_stdv.toFixed(2)
}))

Edit - toFixed will return a string, so add a + to convert it to number

You will need to loop the array of objects, and apply the function you mentioned on each number property.

First you will need to parse that JSON to get the JavaScript Object, and then apply something like this snippet:

const newArray = yourArray.map((obj) => ({
      ...obj,
      value_avg_plus_stdv: +obj.value_avg_plus_stdv.toFixed(2),
      value_avg_minus_stdv: +obj.value_avg_minus_stdv.toFixed(2),
    }));

The + on the toFixed() will convert the strings to numbers

Let's go through your problem step-by-step

1) Get the file

In the further steps I will assume that you have already got the file and read its content into a String, I will call it rawInput from now on.

2) Convert your String into an object

var rawInput = `[
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 3457.7132034355964,
    "value_avg_minus_stdv": 3415.2867965644036
},
{
    "module": "prado2",
    "current_value": 3437.0,
    "value_avg": 3436.5,
    "value_avg_plus_stdv": 4457.7132034355964,
    "value_avg_minus_stdv": 3425.2867965644036
}
]`;
var input = JSON.parse(rawInput);

Now fix your object's items:

input

3) Make the conversion for numeric fields:

for (let item of input)
    for (let att in item)
        if (typeof item[att] === "number") item[att] = item[att].toFixed(2);

4) Convert it back to String:

var output = JSON.stringify(input)

5) Output

"[{\"module\":\"prado2\",\"current_value\":\"3437.00\",\"value_avg\":\"3436.50\",\"value_avg_plus_stdv\":\"3457.71\",\"value_avg_minus_stdv\":\"3415.29\"},{\"module\":\"prado2\",\"current_value\":\"3437.00\",\"value_avg\":\"3436.50\",\"value_avg_plus_stdv\":\"4457.71\",\"value_avg_minus_stdv\":\"3425.29\"}]"

If you just need to truncate the numbers to a specified number of digits here is a mand line tool that does that.

https://pypi/project/jsonvice/

Its written in python but has the logic in it. You can also choose whether to round, truncate or floor the numbers.

disclaimer I'm the author, but I ran in to this issue when pressing large machine learning models.

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