Is it possible to check data in a variable is string or JSON object?
var json_string = '{ "key": 1, "key2": "2" }';
var json_string = { "key": 1, "key2": "2" };
var json_string = "{ 'key': 1, 'key2', 2 }";
When json_string.key2 return 2 or when undefined.
When we need to Use JSON.parse ?
How I check which one is string or JSON object.
because your 3rd json_string is invalid you also have to check for errors:
function checkJSON(json) {
if (typeof json == 'object')
return 'object';
try {
return (typeof JSON.parse(json));
}
catch(e) {
return 'string';
}
}
var json_string = '{ "key": 1, "key2": "2" }';
console.log(checkJSON(json_string)); //object
json_string = { "key": 1, "key2": "2" };
console.log(checkJSON(json_string)); //object
json_string = "{ 'key': 1, 'key2', 2 }";
console.log(checkJSON(json_string)); //string
try this:
if(typeof json_string == "string"){
json = JSON.parse(json_string);
}
typeof json_string == "object"There's not really such thing as a 'JSON object'. Once a JSON string has been successfully decoded it just becomes an object, or an array, or a primitive (string, number, etc.).
However, you probably want to know whether a string is a valid JSON string:
var string1 = '{ "key": 1, "key2": "2" }';
var string2 = 'Hello World!';
var object = { "key": 1, "key2": "2" };
var number = 123;
function test(data) {
switch(typeof data) {
case 'string':
try {
JSON.parse(data);
} catch (e) {
return "This is a string";
}
return "This is a JSON string";
case 'object':
return "This is an object";
default:
return "This is something else";
}
}
console.log(test(string1));
console.log(test(string2));
console.log(test(object));
console.log(test(number));To check variable type, you can use typeof operator
And for converting a valid stringified json object, you can use following function
If a variable is object then it does not do anything and returns same object.
but if it is a string then it tries to convert it to object and returns.
function getJSON(d) {
var jsonObject;
jsonObject = d;
if (typeof d === 'string') {
try {
jsonObject = JSON.parse(d);
} catch (Ex) {
jsonObject = undefined;
console.log("d " ,d, 'Error in parsing', Ex);
}
}
return jsonObject;
};
var obj = {a:2, b:3};
var stringified_obj = JSON.stringify(obj);
console.log(obj);
console.log(getJSON(stringified_obj));You can use the constructor property to verify if a variable contains a stringified JSON or an actual JSON object without using try...catch (it looks kinda ugly I think).
const a = {a: 1, b: 2};
const b = "{a: 1, b: 2}";
function IsJsonOrString(obj) {
if (obj.constructor === ({}).constructor) {
// obj is a JSON
return "JSON";
} else {
// obj is a String
return "STRING";
}
}
console.log(IsJsonOrString(a)); // JSON
console.log(IsJsonOrString(b)); // STRING
Furthermore if you want to verify if the string is a valid parsable JSON string, then you can run JSON.stringify with try...catch but I think you only intend to differentiate between string and json variables.
typeof json_string.