Encountering a problem when verifying if the data is in JSON format using JavaScript

Question

Encountering a problem when verifying if the data is in JSON format using JavaScript

I'm using JavaScript to determine whether an input value is in JSON format, but I've encountered a problem with a specific value. Below is my code explanation.

isJSON = async(str) => {
  try {
    return (JSON.parse(str) && !!str);
  } catch (e) {
    return false;
  }
}

var testJSON = '{"name": "foo"}'
var number = 22
console.log("result is : ", isJSON(testJSON))
console.log("result is : ", isJSON(number))

The variable str holds the input value and this function checks if the value is of json type or not. However, it returns true even for numeric input values like str=22. My intention is to only check if the input value is in the json format. Can you help me resolve this issue?

javascript json

Answer 1

Answer №1

JSON.parse function will automatically convert values to strings.

To ensure that the value is indeed a string, you can perform a simple check.

if (typeof str !== "string") return false;

The text "22" is considered a valid JSON string.

If your goal is to verify not only if the value is in JSON format but specifically a representation of a non-array object, then you need to implement additional checks.

isObjectAsJSON = (str) => {
  if (typeof str !== "string") return false;
  try {
    const parsed = JSON.parse(str);
    if (typeof parsed !== "object") return false;
    if (Array.isArray(parsed)) return false;
    return true;
  } catch (e) {
    return false;
  }
};

const sampleValues = {
  number: 22,
  json_number: JSON.stringify(22),
  json_array: JSON.stringify(["foo", "bar"]),
  json_object: JSON.stringify({
    foo: "bar"
  }),
};

Object.entries(sampleValues).forEach(([key, value]) => {
  console.log(key, isObjectAsJSON(value))
});

Answer 2

JSON.parse function will automatically convert values to strings.

To ensure that the value is indeed a string, you can perform a simple check.

if (typeof str !== "string") return false;

The text "22" is considered a valid JSON string.

If your goal is to verify not only if the value is in JSON format but specifically a representation of a non-array object, then you need to implement additional checks.

isObjectAsJSON = (str) => {
  if (typeof str !== "string") return false;
  try {
    const parsed = JSON.parse(str);
    if (typeof parsed !== "object") return false;
    if (Array.isArray(parsed)) return false;
    return true;
  } catch (e) {
    return false;
  }
};

const sampleValues = {
  number: 22,
  json_number: JSON.stringify(22),
  json_array: JSON.stringify(["foo", "bar"]),
  json_object: JSON.stringify({
    foo: "bar"
  }),
};

Object.entries(sampleValues).forEach(([key, value]) => {
  console.log(key, isObjectAsJSON(value))
});

Answer 3

Answer №2

According to https://www.json.org/json-en.html, the sequence of characters "22" qualifies as valid JSON since JSON follows a specific structure where an element is a WS value WS, and the value in this case can be a number.

Answer 4

According to https://www.json.org/json-en.html, the sequence of characters "22" qualifies as valid JSON since JSON follows a specific structure where an element is a WS value WS, and the value in this case can be a number.

Encountering a problem when verifying if the data is in JSON format using JavaScript

Answer №1

Answer №2

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