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JavaScript Conditionals

Give your programs a brain. Master control flow using if, else, switch statements, and ternary operators.

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Tutor:Programs need to make decisions. Without conditions, a script runs line by line doing the exact same thing every time.


Logic Matrix

UNLOCK NODES BY MASTERING STATEMENTS.

Concept: If / Else

Control the flow by evaluating boolean expressions. If true, run block A. Else, run block B.

System Check

What keyword handles all the logic when an 'if' evaluates to false?

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Written a complex switch statement or a neat ternary trick? Share your JavaScript logic.

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JavaScript Conditionals

Author

Pascual Vila

Frontend Instructor // Code Syllabus

Conditionals are the decision-making foundation of programming. They allow your JavaScript code to behave differently depending on current values, user input, or application state.

if / else if / else

The most common way to write conditional logic is using if, else if, and else. JavaScript evaluates the condition inside the parentheses. If it is truthy, the block of code executes. If not, it skips to the next block.

Switch Statements

When evaluating a single variable against many possible precise values, a switch statement is often cleaner. It uses case blocks to define paths. Remember to include the break keyword to stop execution from "falling through" to the next cases!

Ternary Operator

For simple true/false assignments, the ternary operator is a fast, inline alternative. The syntax condition ? trueResult : falseResult returns a value immediately, making it perfect for assigning variables based on a condition.

View Full Transcript+

This section contains the full detailed transcript of the video lessons for accessibility purposes. Conditionals dictate control flow. We discussed "if", which evaluates a boolean statement. If true, the code block runs. Then "else" provides a fallback. "Else if" lets us chain conditions. We covered "switch" statements as an alternative for strict equality matching against multiple values. Finally, the ternary operator is a shorthand for single-line inline assignments based on a boolean. We also briefly covered what JS considers "truthy" or "falsy" (0, empty strings, null, undefined, NaN, false).

JS Conditionals Glossary

if Statement

Executes a block of code if a specified condition is true.

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else Statement

Executes a block of code if the same condition is false.

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else if

Specifies a new condition to test, if the first condition is false.

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switch Statement

Evaluates an expression, matching the expression's value to a case clause.

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Ternary Operator

A shorthand for an if/else statement. Takes three operands: condition ? exprIfTrue : exprIfFalse.

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Truthy / Falsy

Values that inherently evaluate to true or false in a boolean context. Falsy: false, 0, '', null, undefined, NaN.

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