Small Ideas That Solve Real Problems

Checking if an object is empty requires iterating through its properties manually.

Use Object.keys(obj).length === 0 to quickly check if an object has no properties.

One-line solution that is faster and more reliable than manual iteration.

Calculating percentages like 15% or 18% requires complex mental math.

Break percentages into easy parts: 10%, 5%, 1%. Then combine them.

Calculate any percentage mentally by breaking it into simple components.

Removing null, undefined, 0, false, NaN from arrays requires complex conditional logic.

Use Array.filter(Boolean) to remove all falsy values in one line.

Eliminates 10+ lines of conditional logic and handles all falsy values automatically.

Testing if large numbers are divisible by 3 requires actual division.

Sum all digits. If the sum is divisible by 3, the number is divisible by 3.

Instant divisibility test without performing division.

Functions need fallback values when parameters are not provided, requiring manual checks.

Use default parameter syntax to automatically assign fallback values in function signatures.

Reduces defensive coding by 50% and makes function interfaces self-documenting.

Checking divisibility by 9 for large numbers requires long division.

Sum all digits. If the sum is divisible by 9, the number is divisible by 9.

Quick mental check for divisibility by 9 without calculation.

Copying arrays with traditional methods can accidentally create references instead of new arrays.

Use the spread operator [...arr] to create a shallow copy of an array.

Prevents mutation bugs and creates independent copies in one simple syntax.

Finding square roots mentally for non-perfect squares is difficult.

Find the two perfect squares it falls between, then estimate proportionally.

Get accurate estimates (±0.5) of square roots mentally in seconds.