What can be done to avoid JSON.stringify from returning undefined in a specific scenario, which in turn leads to a string that fails when parsed by JSON.parse

Question

What can be done to avoid JSON.stringify from returning undefined in a specific scenario, which in turn leads to a string that fails when parsed by JSON.parse

Running Windows 7 64 bit with Firefox version 32, I came across the issue that JSON.parse cannot handle JSON.parse("{ 'a': undefined }";
Surprisingly, when I use JSON.stringify in a specific scenario, I end up with undefined:

console.log("'abc': " + JSON.stringify(this.nothing));

This code snippet results in:

"'abc': undefined"

In my custom functions where I create object-strings, I opt for using JSON.stringify to simplify certain variables. I thought this would guarantee security, but obviously not.

javascript json firefox windows-7 undefined

Answer 1

Answer №1

Your utilization of the JSON feature is incorrect:

console.log(JSON.stringify({ abc: this.nothing }));

This will result in the JSON string "{}", which is accurate since ({}).abc returns undefined. The JSON specification does not allow for undefined; only strings, numbers, booleans, and null are permitted as scalar values. Therefore, a JavaScript property with an undefined value is represented as if it does not exist within the object at all.

Avoid using JSON.stringify() piece by piece. Construct your JavaScript object structure first before converting the entire thing into a string.

Answer 2

Your utilization of the JSON feature is incorrect:

console.log(JSON.stringify({ abc: this.nothing }));

This will result in the JSON string "{}", which is accurate since ({}).abc returns undefined. The JSON specification does not allow for undefined; only strings, numbers, booleans, and null are permitted as scalar values. Therefore, a JavaScript property with an undefined value is represented as if it does not exist within the object at all.

Avoid using JSON.stringify() piece by piece. Construct your JavaScript object structure first before converting the entire thing into a string.

Answer 3

Answer №2

When using JSON.stringify, values that are not supported cannot be turned into JSON. One example of an unsupported value is undefined.

For instance, if you use JSON.stringify(null), you will receive the string "null" as null is a supported value. The list of supported values can be found at http://json.org/.

However, when you try to use JSON.stringify(undefined), you will not get back the string "undefined". Instead, the unsupported value is excluded from the result, resulting in an empty output. In this case, the output will be the value undefined.

Answer 4

When using JSON.stringify, values that are not supported cannot be turned into JSON. One example of an unsupported value is undefined.

For instance, if you use JSON.stringify(null), you will receive the string "null" as null is a supported value. The list of supported values can be found at http://json.org/.

However, when you try to use JSON.stringify(undefined), you will not get back the string "undefined". Instead, the unsupported value is excluded from the result, resulting in an empty output. In this case, the output will be the value undefined.

What can be done to avoid JSON.stringify from returning undefined in a specific scenario, which in turn leads to a string that fails when parsed by JSON.parse

Answer №1

Answer №2

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