JavaScript's implicit global variables can cause unpredictable behavior by making variables accessible from anywhere in their scope without being explicitly declared with `var`, `let`, or `const`. This can lead to naming conflicts, unclear intent, and unintended consequences, making code harder to understand and maintain. Using strict mode, explicit variable declarations, and module-based encapsulation can help avoid these pitfalls.
Implicit global variables in JavaScript can cause problems like name collisions, scope pollution, security risks, and reduced code readability. To avoid these issues, use `var`, `let`, or `const` declarations, enable strict mode, and utilize a linter or code analyzer to detect and prevent implicit global variables.
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