Always use strict equality (=== and !==) in JavaScript to avoid unexpected behavior from type coercion. 1. Loose equality (==) can lead to counterintuitive results because it performs type conversion, making 0 == false, "" == false, "1" == 1, and null == undefined all true. 2. Strict equality compares both value and type, ensuring predictable outcomes: 0 === false, "" === false, "1" === 1, and null === undefined are all false. 3. Use === in form validation, API handling, configuration checks, and state comparisons to prevent subtle bugs. 4. Prefer === and !== by default, validate input types early, and consider TypeScript for compile-time type safety. 5. Avoid truthiness checks when exact values are needed; instead of if (user.role), use if (user.role === "admin"). 6. For null or undefined checks, value == null is acceptable and commonly used because it reliably covers both. 7. Handle special cases: use Number.isNaN() for NaN checks since NaN !== NaN, and use deep comparison tools like Lodash’s _.isEqual() for object and array value comparisons. 8. Proactively manage edge cases to ensure conditionals behave as intended. Strict equality is not a complete solution but is essential for reliable, bug-free logic. In JavaScript, if it’s not ===, it’s a gamble.

When writing conditionals in JavaScript (or any loosely typed language), unexpected behavior can creep in if you're not careful with type comparisons. The key to crafting bulletproof conditionals lies in using strict equality (=== and !==) instead of loose equality (== and !=). Here's why it matters and how to apply it effectively.

Why Loose Equality Is Risky

JavaScript’s loose equality (==) performs type coercion before comparison. That means values of different types can be considered equal, which often leads to counterintuitive results:

0 == false   // true
"" == false  // true
"1" == 1     // true
null == undefined // true

These might seem convenient, but they open the door to bugs, especially when dealing with user input, API responses, or form data where types aren't guaranteed.

Use Strict Equality for Predictable Results

Strict equality (===) checks both value and type, eliminating surprises:

0 === false   // false
"" === false  // false
"1" === 1     // false
null === undefined // false

By using ===, you ensure your conditionals behave consistently. This is especially important in:

• Form validation
• API response handling
• Configuration checks
• Feature flags or state comparisons

For example:

function isActive(status) {
  return status === "active"; // Only matches string "active"
}

Without strict comparison, isActive(1) could return true if loosely compared to "1"—a subtle bug that’s hard to catch.

Practical Tips for Bulletproof Conditionals

To make your logic resilient:

• Always prefer === and !== unless you explicitly need type coercion (rare).

• Validate input types early in functions, especially when dealing with external data.

• Use TypeScript to catch type issues at compile time, reducing runtime surprises.

• Avoid truthiness checks when specific values are expected:

  // Risky
  if (user.role) { ... }
  
  // Better
  if (user.role === "admin") { ... }

• When checking for null or undefined, use:

  value === null || value === undefined
  // or shorthand (if you're okay with coercion here)
  value == null

  The == null pattern is widely accepted for nullish checks because it's predictable and concise.

Handle Edge Cases Proactively

Some values in JavaScript are notoriously tricky:

• NaN never equals itself, even with ===. Use Number.isNaN() instead.

• Objects (including arrays and dates) are compared by reference, not value:

  [1,2] === [1,2] // false

  For deep comparisons, use helper functions or libraries like Lodash’s _.isEqual().

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  Using strict comparisons doesn’t make your code bulletproof on its own—but it’s a foundational step. Combined with good type discipline and defensive checks, it ensures your conditionals behave exactly as intended.

  Basically: if it’s not ===, it’s a gamble.

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