This question explores JavaScript and addresses practical considerations related to: Why does 'this' inside a function behave differently in strict mode?

Why does 'this' inside a function behave differently in strict mode?

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Why does 'this' inside a function behave differently in strict mode?

Asked on Jan 22, 2026

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In JavaScript, "this" inside a function behaves differently in strict mode because strict mode enforces a more predictable and safer set of rules. In non-strict mode, "this" defaults to the global object, but in strict mode, "this" becomes "undefined" if not explicitly set.

<!-- BEGIN COPY / PASTE -->
        function nonStrictFunction() {
            console.log(this); // Logs the global object (window in browsers)
        }
        nonStrictFunction();

        function strictFunction() {
            'use strict';
            console.log(this); // Logs undefined
        }
        strictFunction();
        <!-- END COPY / PASTE -->

Additional Comment:

In non-strict mode, calling a function without a specific context sets "this" to the global object.
In strict mode, "this" is "undefined" when a function is called without a specific context.
Using strict mode helps prevent accidental modifications to the global object and can catch common coding errors.

✅ Answered with JavaScript best practices.

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Why does 'this' inside a function behave differently in strict mode?

Asked on Jan 22, 2026

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