How to check if a string is a valid JSON string in JavaScript without using Try/Catch

Question

Something like:

var jsonString = \'{ \"Id\": 1, \"Name\": \"Coke\" }\';

//should be true
IsJsonString(jsonString);

//should be false
IsJsonString(\"foo\");         


        

Answer 1

// vanillaJS
function isJSON(str) {
    try {
        return (JSON.parse(str) && !!str);
    } catch (e) {
        return false;
    }
}

Usage: isJSON({}) will be false, isJSON('{}') will be true.

To check if something is an Array or Object (parsed JSON):

// vanillaJS
function isAO(val) {
    return val instanceof Array || val instanceof Object ? true : false;
}

// ES2015
var isAO = (val) => val instanceof Array || val instanceof Object ? true : false;

Usage: isAO({}) will be true, isAO('{}') will be false.