How can I convert a JSON string to an object in JavaScript?

Assuming we got the JSON syntax right, your string:

var s = '{"nombre":"juan"}';

It's already JSON! , you don't need any conversion.

JSON notation is a way to serialize a JavaScript object into a string, so you already have JSON.

Note : You can write it (without the s variable and without the single quotes: {"nombre":"juan"}) in this page: Json Parser Online to validate it.

Now if you want to convert it to a JavaScript object.

var o = JSON.parse(s);

and return it to JSON:

var json = JSON.stringify(o);

Finally, as @ratlab mentions, if your browser does not support the object, JSONyou can use a library like json2.js or JSON 3

Or use this polyfill from MDN directly in your code:

if (!window.JSON) {
    window.JSON = {
        parse: function(sJSON) { return eval('(' + sJSON + ')'); },
        stringify: (function () {
            var toString = Object.prototype.toString;
            var isArray = Array.isArray || function (a) { return toString.call(a) === '[object Array]'; };
            var escMap = {'"': '\\"', '\\': '\\\\', '\b': '\\b', '\f': '\\f', '\n': '\\n', '\r': '\\r', '\t': '\\t'};
            var escFunc = function (m) { return escMap[m] || '\\u' + (m.charCodeAt(0) + 0x10000).toString(16).substr(1); };
            var escRE = /[\\"\u0000-\u001F\u2028\u2029]/g;
            return function stringify(value) {
                if (value == null) {
                    return 'null';
                } else if (typeof value === 'number') {
                    return isFinite(value) ? value.toString() : 'null';
                } else if (typeof value === 'boolean') {
                    return value.toString();
                } else if (typeof value === 'object') {
                    if (typeof value.toJSON === 'function') {
                        return stringify(value.toJSON());
                    } else if (isArray(value)) {
                        var res = '[';
                        for (var i = 0; i < value.length; i++)
                            res += (i ? ', ' : '') + stringify(value[i]);
                        return res + ']';
                    } else if (toString.call(value) === '[object Object]') {
                        var tmp = [];
                        for (var k in value) {
                            if (value.hasOwnProperty(k))
                                tmp.push(stringify(k) + ': ' + stringify(value[k]));
                        }
                        return '{' + tmp.join(', ') + '}';
                    }
                }
                return '"' + value.toString().replace(escRE, escFunc) + '"';
            };
        })()
    };
}

Note : Now that I investigate a little more, of the 3 libraries mentioned above, json2.js, JSON 3and the pollyfill, I only recommend JSON 3 . The reason is that the pollyfill is just a probably unsupported code sample and json2.jsdespite being the original library, it is an old library, with some bugs and it does not match the current standard. More information in the Changes from JSON 2 section of the JSON 3 documentation

In JavaScript there are 2 methods to convert from string with JSON notation to object and vice JSON.parseversa JSON.stringify:

var obj1 = 'null';
var obj2 = '1';
var obj3 = '"string"';
var obj4 = '[1,2,3]';
var obj5 = '{"double_quote": "any object"}'

console.log(JSON.parse(obj1)); => null
console.log(JSON.parse(obj2)); => 1
console.log(JSON.parse(obj3)); => "string"
console.log(JSON.parse(obj4)); => [1,2,3]
console.log(JSON.parse(obj5)); => {"double_quote": "any object"}

console.log(JSON.stringify(obj3)) => "\"string\""

You should keep in mind that null, true, falseare also valid JSON values ​​and that character strings must include a double quote at the beginning and end of the string to be considered as such, otherwise they will be interpreted as other data types. Regular expressions and functions are not as JSON is a data exchange format and the latter are considered "code".

You can find the full specification of the format here and also on the json.org page itself.

These features are supported in most browsers Chrome, Firefox 3.5+, Internet Explorer 8+, Opera 10.5+ and Safari 4.0+.

If it is not present, you can use the JSON2 library made by Douglas Crockford himself , the creator of this format, based on existing JavaScript structures.

Taking into account your initialization code:

var myString = "{'nombre':'juan'}";

Solution

Use of language intrinsic tools: JSON.parse()

var objeto = JSON.parse(myString);

The MDN documentation tells us that:

JSON.parse(text[, reviver]) : The JSON.parse() method parses a text string as JSON, optionally transforming the value produced by the parse.

Using the word "JSON object" and "JSON text" may be a pleonasm but in reality it is so common that when it is expressed in that way it gives a whole context to the recipient of the message other than just using JSON.

This can be seen on the page: JSON in JavaScript .

var myJSONObject ... To convert a JSON text into an object ...

Add to @dabbbb's answer.

which browsers like:

• ie8 forward.
• firefox
• Chrome

they have native support for JSON, in case you need to do this in older browsers you will need to include JSON2