javascript is json string valid

1function IsJsonString(str) {
2    try {
3        JSON.parse(str);
4    } catch (e) {
5        return false;
6    }
7    return true;
8}

1function isValidJSONString(str) {
2    try {
3        JSON.parse(str);
4    } catch (e) {
5        return false;
6    }
7    return true;
8}
9//usage
10var personJSONString = '{"first_name":"Tony","last_name":"Hawk","age":31}';
11if(isValidJSONString(personJSONString)){
12 //cool we are valid, lets parse
13 var person= JSON.parse(personJSONString);
14}
15

1//extensive check to make sure object is not of string type and not null
2function isJson(item) {
3    item = typeof item !== "string"
4        ? JSON.stringify(item)
5        : item;
6
7    try {
8        item = JSON.parse(item);
9    } catch (e) {
10        return false;
11    }
12
13    if (typeof item === "object" && item !== null) {
14        return true;
15    }
16
17    return false;
18}