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Javascript – Why should this code be expecting a comma?

I am watching this course focused on programming for beginners. So, the instructor wrote the following code:

let numberOfLines = 1;

console.log(`Line #`, numberOfLines);

My question is, why do I get an error if I do not put the comma (,) before "numberOfLines"?
If I don’t write it, it sends me a message about expecting it to be added.

I tried writing the code without a comma, just for curiosity, which resulted in an error. Please, can anyone explain why it happens?

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3

Answers


  1. 0

    In JavaScript, when you use template literals (strings enclosed in backticks “), you can insert variables or expressions inside them using ${}. However, if you want to concatenate a variable or an expression directly without any surrounding text, you should use ${} directly after some text or another ${} expression.

    In your code snippet:

    console.log(`Line #`, numberOfLines);

    You’re using a template literal with backticks, and then you’re trying to directly append numberOfLines without any text or expression preceding it. This is not the correct syntax for template literals. Instead, you should concatenate numberOfLines using ${} like this:

    console.log(`Line #${numberOfLines}`);

    Here, numberOfLines is directly concatenated with the text "Line #" using ${} inside the template literal.

    So, the correct usage of template literals in this context requires you to use ${} to interpolate variables or expressions within the template literal.

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  2. 0 
    console.log(`Line #`, numberOfLines);

    This code calls the log function on the console object. It provides two arguments to that function. "Line #" is the first argument, and numberOfLines is the second argument.

    And a , is how you separate arguments in a function invocation. You need a comma between all function arguments so that javascript knows where one argument ends, and the next one begins.

    It just part of the grammar of the language. You get an error without the comma because the language specification says that one is required. It’s as simple as that.

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  3. 0

    console.log() is a function. A function has a set list of parameters that it expects. If you remove the comma, JavaScript does not know what you are trying to do – It thinks you are trying to pass 2 values for one single argument.

    With the comma, JavaScript knows you are wanting to pass the value before the comma as the first argument, and the value after the comma as the second argument.

    This link may be useful: Read More about console.log()
    Hope this helps!

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