What is the reason behind obtaining a distinct outcome when logging the properties of an object compared to logging the object itself and checking its properties?

Question

What is the reason behind obtaining a distinct outcome when logging the properties of an object compared to logging the object itself and checking its properties?

Currently, I am working on integrating socket-io with react redux and encountering a peculiar namespace problem.

console.log(socket);
console.log(socket.disconnected);
console.log(socket.id);
console.log(socket);

The first log displays a comprehensive object with two key properties:

disconnected: false;
id: PuAi01tcCcZgmJaAACM

However, the second and third logs provide different results. When logging socket.disconnected, it returns true, and when logging socket.id, it shows undefined.

To ensure consistency, I added another log. Surprisingly, it displays the initial object where disconnected is false and id exists.

This situation appears to be related to a perplexing namespace problem. It seems like there are two distinct versions of the socket name, causing confusion when accessing its properties.

javascript

Answer 1

Answer №1

Solution

To prevent the live updating of the log for your object in modern browsers, convert your object to a string before logging it:

const example = { foo: 'bar' };
console.log(JSON.stringify(example));
// or with pretty printing: 
console.log(JSON.stringify(example, null, 2));

Explanation

In modern browsers, console.log does not display a string, but rather a reference to the actual JavaScript object in memory. Thus, by the time the logged object is viewed, all JavaScript operations have already been executed and the object has changed.

const example = { foo: 'bar' };
console.log(example);
example.foo = 'baz';
// log will show { foo: 'baz' } (usually indicating that the value is live)

When logging an object's property, if that property is immutable (such as a string, boolean, or number), the console will display the value of the object instead of a reference. Consequently, altering a string after logging it will not affect the original string displayed in the console.

let example = 'foo';
console.log(example);
example = 'bar';
// log will show 'foo'

Answer 2

Solution

To prevent the live updating of the log for your object in modern browsers, convert your object to a string before logging it:

const example = { foo: 'bar' };
console.log(JSON.stringify(example));
// or with pretty printing: 
console.log(JSON.stringify(example, null, 2));

Explanation

In modern browsers, console.log does not display a string, but rather a reference to the actual JavaScript object in memory. Thus, by the time the logged object is viewed, all JavaScript operations have already been executed and the object has changed.

const example = { foo: 'bar' };
console.log(example);
example.foo = 'baz';
// log will show { foo: 'baz' } (usually indicating that the value is live)

When logging an object's property, if that property is immutable (such as a string, boolean, or number), the console will display the value of the object instead of a reference. Consequently, altering a string after logging it will not affect the original string displayed in the console.

let example = 'foo';
console.log(example);
example = 'bar';
// log will show 'foo'

What is the reason behind obtaining a distinct outcome when logging the properties of an object compared to logging the object itself and checking its properties?

Answer №1

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