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Transform values from a JSON representation

Topics: JavaScript

When transforming a given variable to the JSON representation, we might see unexpected results if the variable contains an unserializable property.

Let's consider a simple object that represents the information of a person. It has the phones property that is a set of different phone numbers.

const person = {
name: 'John Doe',
ages: 42,
phones: new Set(['123', '456', '789']),

The set is transformed to an empty object which is unexpected output:


// "{"name":"John Doe","ages":42,"phones":{}}"

We can solve the issue by passing the second parameter to the stringify function. It can be a function of two parameters representing the key and value of the current iterated item.

JSON.stringify(variable, (key, value) => {
// The return value will be used in final output

// If the function returns `undefined`,
// the item will be excluded from the output
return ...;

Here is how the phone numbers are transformed when we see the phones key:

JSON.stringify(person, (key, value) => (
(key === 'phones') ? [...value.values()] : value

// "{"name":"John Doe","ages":42,"phones":["123","456","789"]}"

Want to transform all Set values? No problem!

JSON.stringify(person, (key, value) => (
(value instanceof Set) ? [...value.values()] : value


Fix a typo or suggest an improvement
#126 Create shapes with the clip path property