Why '5' - true Equals 4 in JavaScript – Type Coercion Explained! Understanding JavaScript Type Coercion. Asked in TCS interview.

This is a classic example of type coercion in JavaScript, especially when working with different data types in an arithmetic operation.

Here’s your code:

let x = "5";
let y = true;
console.log(x - y);

Let’s break it down step-by-step like a pro teacher:

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Step 1: Variable Declarations :-

let x = "5";

• x is a string, holding the text "5", not the number 5.

let y = true;

• y is a boolean, holding the value true.

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Step 2: The Expression — x - y :-

Now we evaluate:

"5" - true

🔸 What Happens Behind the Scenes?

In JavaScript, the - operator only works on numbers, so JavaScript automatically converts both operands into numbers using type coercion:

1. "5" → Number
• A string "5" is coerced to the number 5.
2. true → Number
• The boolean true is coerced to 1 (and false would be 0).

👉 So this becomes:

5 - 1

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Step 3: The Result :-

5 - 1 = 4

So the final output is:

console.log(4); // →  4
✔ Final Answer:
A) 4
This question appeared in the TCS 2nd round of interview, testing the candidate’s knowledge of type coercion between numeric string and number when we negate them in JavaScript.