Selection

• Use if/else selection statements in JavaScript
• Use switch selection statements in JavaScript
• Use the conditional operator

• W3Schools.com article on conditional statements
• Mozilla article on if...else statements

Examples:

if (expr) { ... code executed if expr is true ... } if (expr) { ... code executed if expr is true ... } else { ... code executed if expr is false ... } if (expr) { ... code executed if expr is true ... } else if (expr2) { ... code executed if expr is false and expr2 is true ... } else { ... code executed if expr is false and expr2 is false ... }

Mozilla article on switch statements

Example:

switch (expr) { case value1: ... code executed if expr==value1 ... break; case value2: ... code executed if expr==value2 ... break; . . . default: ... code executed if no case values matched expr }

• The conditional operator "?:" takes three operands. If the first operand evaluates to true, the entire expression assumes the value of the second operand. If the first operand evaluates to false, the entire expression assumes the value of the third operand.
• The || (OR) operator can be used to choose an alternative value for an expression if a primary value evaluates to false.

Example:

// demonstration of conditional to get maximum value var x = 7, y = 24; var max = x > y ? x : y; // conditional: x > y ? x : y // demonstration of using OR to choose an alternate value var name = "" || "Unidentified"; // name will be "Unidentified" since first value evaluates to false

• demonstration of simple if statements
• demonstration of nested if/else statements
• demonstration of switch statement
• demonstration of compressed if/else statements