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Unexpected Behind The Scenes of console.log() 😶‍🌫

Arjun Vijay Prakash on February 08, 2024

🤔 Have you ever thought about how console.log works and how it can handle many arguments at once? If you’ve worked with JavaScript, then...

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James Livesey • Feb 9 '24

Not to mention that arguments is a reserved word to get all the arguments passed to a function as an iterable object (including arguments already named) without having to use the spread operator in the function's parameters list:

function test(a, b, c) {
    console.log("All arguments:", arguments);

    // We must use the spread operator to use `forEach` as `arguments` is an object with other properties in it
    [...arguments].forEach(function(arg) {
        console.log(arg);
    });
}

test("hello", 123, "world", 456, null);

Result:

All arguments: ["hello", 123, "world", 456, null]
hello
123
world
456
null

(Notice how arguments contains extra arguments than explicitly specified with the named a, b and c parameters.)

Arjun Vijay Prakash • Feb 10 '24

This is amazing! Thanks for the info, James. 🙌

BestCodes • Feb 8 '24

Great article! Browsers and even the simplest things in JS really are amazing. (For that matter, that we can turn sand into silicon and silicon into computers).
Keep up the good writing!