In order to check the validity of a string whether it is a JSON string or not, We’re using the JSON.parse()method with a few variations. JSON.parse() This method parses a JSON string and constructs the JavaScript value or object specified by the string. A reviver function may be provided to do a change on the resulting object before it’s returned. It can be done using the following methods:
Methods to Check if a String is Valid JSON String:
- Using JSON.parse() method
- Using JSON.stringify() method
Method 1: Using JSON.parse() method
The JSON.parse() method in JavaScript is used to parse a JSON string which is written in a JSON format and returns a JavaScript object.
Syntax:
JSON.parse( text, function)
Example 1: This example checks the validity of JSON string by JSON.parse() method by creating a function.
Javascript
// Input stinglet str = '{ "prop_1": "val_1", "prop_2": "val_2" }';console.log("Input string is : " + str);// Function to test stringfunction testJSON(text) { if (typeof text !== "string") { return false; } try { JSON.parse(text); return true; } catch (error) { return false; }}// Function to display outputfunction gfg_Run() { console.log(testJSON(str));}// Function callgfg_Run(); |
Input string is : { "prop_1": "val_1", "prop_2": "val_2" }
true
Example 2: This example is returning false because the property value val_1 is not a string.
Javascript
// Input stinglet str = '{ "prop_1": val_1, "prop_2": "val_2" }';console.log("Input string is : " + str);// Function to test stringfunction isJSON(str) { try { return JSON.parse(str) && !!str; } catch (e) { return false; }}// Function to display outputfunction gfg_Run() { console.log(isJSON(str));}// Function callgfg_Run(); |
Input string is : { "prop_1": val_1, "prop_2": "val_2" }
false
Example 3: This example is returning true by using the JSON.parse() method along with typechecking of the text.
Javascript
// Input stinglet str = '{ "prop_1": 1, "prop_2": "val_2" }';console.log("Input string is : " + str);// Function to test stringfunction isJSON(str) { try { return JSON.parse(str) && !!str; } catch (e) { return false; }}// Function to display outputfunction gfg_Run() { console.log(isJSON(str));}// Function callgfg_Run(); |
Input string is : { "prop_1": 1, "prop_2": "val_2" }
true
Method 2: Using JSON.stringify() method
The JSON.stringify() method in Javascript is used to create a JSON string out of it.
Syntax:
JSON.stringify(value, replacer, space);
Example: In this example, we will try to convert the given object to a string using JSON.stringify() method
Javascript
// Input stinglet str = '{ "prop_1": val_1, "prop_2": "val_2" }';console.log("Input string is : " + str);// Function to test stringfunction isJSON(str) { try { JSON.stringify(JSON.parse(str)); return true; } catch (e) { return false; }}// Function to display outputfunction gfg_Run() { console.log(isJSON(str));}// Function callgfg_Run(); |
