What does the blue digit in the Chrome Developer Console indicate?

I encountered a strange situation in JavaScript where I have a variable that I log to console.log, then increment it and log it again. The Chrome Dev Tools display the following result.

This variable has shown some odd behavior, such as using the += operator to add to it resulting in the added value appearing after the number (for instance, if x=5 and I perform x+=3, x becomes 53). What puzzles me is that while incrementing with ++ functions correctly, I am curious about why the incremented number appears in blue in the console. If anyone could provide insights on scenarios where this may occur, I would appreciate it. However, I suspect the blue entry in the console is somehow linked to this issue.

In summary, why does a number appear in blue in the Chrome Dev Console?

javascriptvariablesgoogle-chrome-devtoolsincrement

Answer №1

Output in console.log appears black when displaying strings, but turns blue for numbers. Check out the image below (ignore the 'undefined' lines as that's the default return value of console.log()).

Your issues with += are indeed related to these color changes. You were trying to add a number to a string, resulting in concatenation (53).

Answer №2

It's important to understand the distinction between using commas and plus signs in console.log()

console.log( 'console.log("(" + 1 + ")"); // string concatenation' );
console.log("( " + 123 + " )");

console.log( 'console.log("(", 1, ")"); // string, number (blue), string' );
console.log("(", 123, ")");

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