#8 What is strict mode in JavaScript?

Strict Mode in JavaScript is a way to opt in to a restricted version of JavaScript, helping you write more secure, error-free code.

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🔹 How to Enable Strict Mode:

Place "use strict"; at the beginning of a script or a function:

"use strict";

function test() {
  // code runs in strict mode
}

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✅ Key Features of Strict Mode:

• Prevents usage of undeclared variables.
• Makes assignments to read-only properties throw errors.
• Disallows duplicate parameter names in functions.
• Disables with statement.
• Throws error on assigning to non-writable global variables like NaN.
• Makes this inside functions default to undefined instead of the global object.

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❌ Without Strict Mode:

x = 10; // No error, implicitly creates global variable

✅ With Strict Mode:

"use strict";
x = 10; // ❌ ReferenceError: x is not defined

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📝 In Summary:

Strict mode makes JavaScript code more robust by catching common mistakes early and preventing unsafe actions—it's a best practice to use it, especially in large or team-based projects.