JavaScript Tutorial
Conditional logic controls application flow based on runtime state and input values.
Why this matters
Accurate conditions are required for validation, permissions, UI rendering, and business rules.
if/else is ideal for branching where conditions are dynamic and expressive checks are needed.
Order matters in chained conditions. Place most specific checks before generic checks.
Guard clause style (early return) keeps complex functions easier to read.
switch works well for discrete values like status codes or command routing.
Always include default for fallback behavior and safer future handling.
Use break to prevent unintended fallthrough unless fallthrough is explicit and documented.
function accessMessage(role, active) {
if (!active) return "Account inactive";
if (role === "admin") return "Full access";
if (role === "editor") return "Edit access";
return "Read only";
}
console.log(accessMessage("editor", true));Guard clauses simplify control flow and reduce nesting.
function colorByStatus(status) {
switch (status) {
case "success":
return "green";
case "warning":
return "orange";
case "error":
return "red";
default:
return "gray";
}
}
console.log(colorByStatus("warning"));switch is clear for finite known values.
const score = 77;
let label = "";
if (score >= 90) label = "Excellent";
else if (score >= 75) label = "Good";
else label = "Needs Improvement";
console.log(label);Readable style for multi-tier scoring logic.
Always add default to avoid undefined behavior for unknown values.
Use guard clauses and smaller helper functions.
Place specific checks before broad checks.
Use switch when matching one variable against many fixed values.
Not always, but deep nesting hurts readability and maintainability.
Yes, braces improve clarity and reduce accidental bugs in future edits.
Use lookup maps, helper functions, or split logic into dedicated modules.