reading-notes

Class Eight Notes

Loops

Lecture

• for loops: evaluate a preset amount of times before breaking
• while loops: evaluate an infinetely amount of times

Expressions and Operators¹

• Operator Operand form: prefix unary operator (most cases in JavaScript, ex. !, typeof)
• Operand Operator form: postfix unary operator (only ++ and -- in JS)
• if an expression evaluate to an object, the left-hand side of an assginment expression may make assignments to properties of that expression
• Destructuring: extract data from arrays or objects using a syntax that mirrors the construction (ex. const one = foo [0], const two = foo[1], with destructing: const [one, two] = foo)
• Right Associative: evaluates from left to right
• (Expressions) this refers to current object;
• (Expressions) Grouping Operator: () Parentheses creates a grouped expression; new create an instance of a user-defined object type; super call functions on an object’s parent

Loops²

• doing something repeadly -for statement:

for ([initialExpression];[conditionExpression];[incrementExpression]) statement

• for ... in statement ()

for (variable in object) statement

• note: for an Array, it is better to use for instead of for...in, since the name of user-defined properties in additional to the numeric indexes will be returned

• do...while statement: repeats until a specified condition evaluates to false

do, is the condition is false, statement within the loop stops executing statement //always executed ONCE before the condition is checked, use {} to group the statements while (condition); //further executes if returned true

• while: condition test occurs before statement

while (condition) statement

• break statement: terminate a loop. Can be used with a label (terminates the specified labeled statement) or without labels (terminates the innermost enclosing while, do-while, for, or switch)

• continue statement: restart a loop (can be used with or without label)

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References

1. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators ↩

2. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Loops_and_iteration ↩