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

#webdev #javascript #watercooler #discuss

🤔 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 you must have used the console.log method.

It's a function that can accept any number of arguments and print them in the console.

console.log(n1, n2, n3, n4.....n)

😮 But have you wondered how it handles these variable number of arguments?

Well, such functions are also known as variadic functions and you can create them in JavaScript using the rest operator(...).

Let's consider an example of a function written to calculate the sum of n numbers.

First, you create a function using the rest operator to collect all arguments into an array.

This allows an unlimited number of arguments to the function.

(To be honest, there's always some limit, try finding out and comment below as a sign you read the article!)

let sum = (...args) => {
    console.log(args)
}

sum(1, 2, 3, 4, 5, 6);
sum(0);
sum(10, 20, 30);

When the function is called, observe this keyword args captures the arguments as an array.

Once you have this array of values you can continue writing the code to print the sum.

let calculateSum = (...numbers) => { 
    console.log(numbers.reduce((total, num) => total + num))
} 

calculateSum(1, 2, 3, 4, 5, 6); 
calculateSum(0); 
calculateSum(10, 20, 30);

Comment below the theories you thought were behind this functionality! (Believe it or not! I thought it was some kind of miracle 😂)

I hope you liked the article! ❤️

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Happy Coding! 🚀
Thanks for 14415! 🤗

Top comments (11)

James Livesey • Feb 9

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

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

Best Codes • Feb 8

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!