Exploring the world of JSON manipulation in JavaScript

I've been experimenting with JSON recently and came across something I don't quite understand. Here is an example of some code I used:

var str = "{'name':'vvv'}";                    
var cjson = eval ("(" + str + ")");
alert(cjson.name);

That code works well, but when I tried this piece of code:

var str = "{'name':"+'vvv'+"}";    
var cjson = eval ("(" + str + ")");
alert(cjson.name);

It didn't work, and I received the following error in Firebug: ReferenceError: vvv is not defined.

What's causing it to fail in the second example? Shouldn't 'str' be a valid string in both cases?

javascriptjson

Answer №1

Indeed, it is a string, but not the exact same string, and definitely not valid JSON.

 var str = "{'name':" + 'vvv' + "}";

can be interpreted as:

 var str = "{'name':" + "vvv" + "}";

which can also be seen as:

 var str = "{'name':vvv}";

When attempting to process this, it's similar to having defined:

 var cjson = { 'name': vvv };

without an existing variable called vvv.

Answer №2

When using var str = "{'name':"+'vvv'+"}";, the resulting string is "{'name':vvv}" where vvv is not treated as a string literal. Consequently, when evaluated, it will attempt to resolve in the current execution scope and since it's not defined there, an error will be thrown.

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