Unit 8: Operators & Loops

Loops & Iteration in Javascript

Loops

• Repeated actions with beginning and ending points determined by statements:
  • for
  • do…while
  • while
  • labeled
  • break
  • continue
  • for…in
  • for…of

for Statements

• Loop until condition evaluates as false.
• Anatomy: for, followed by two/three paranthetical expressions separated by semicolons, then a statement. Like:
• `for (let a = 200; a > previousvariablehere; a = a / 2)
• let cutstatus = ‘halved’ `
• The initial expression: first paranthetical. This executes, and can declare variables
• The condition expression: second paranthetical. This is evaluated, and if true loop executes. If false, for terminates (note:w/out condition statement, executes as if true)
• The statement: executes. Can group multiple in the same curled brackets
• The increment expression: executes if present
• Loop returns to condition expression

while Statements

• Executes as long as condition evaluates true
• Anatomy: while, followed by paranthetical condition, then statement. Like: `while (condition) statement’
• The condition is tested before execution. If true, statement executes and condition is tested again. If false, loop terminates and passes to statement
• Multiple statements can be blocked together in curly brackets
• Note: make sure condition eventually returns false – otherwise loop is infinite