Control Flow

More on Comparison

• Objects are converted to primitive types if compared with a primitive

• Objects are compared according to their memory address (by reference, much like is in Python)

Control Structures

Block Statements

Conditionals

{
  anything goes here
}

• If/Else

    if(stuff()) {
      //stuff
    } else if (other_stuff()) {
      //other stuff
    } else {
      even more stuff
    }
  

• Switch Statements
  • Fallthrough as in C++
  • can use strings

  switch(expr) {
    case label1:
      statement;
    case label2:
      statement;
      break;
  
    // other cases could be included
  
    default:
      statement;
  }
  

Looping Constructs

For loops

for(let i=0;i<10;i++) {
  // i exists
}
// i does not exist

Do-While

do {
  // stuff
} while(expr);

While

while(expr) {
  // stuff
}

For..in

• iterates over all enumerable and distinct properties of an object in original insertion order

  let obj = {b:2, c:3};
  obj.a = 1;
  for(let x in obj) {
    console.log(x);
  }
  // b
  // c
  // a

  lst = ['h', 'e', 'l', 'l', 'o'];
  lst.name = 'hello';
  for(let x in lst) {
    console.log(x)
  }
  // 0
  // 1
  // 2
  // 3
  // 4
  // 'name'

this weirdness is because for..in iterates over enumerable elements, like indicies

For..Of

• iterates over elements of an iterable object including Array and string

  let arr = [3, 5, 7];
  arr.foo = 'bar';

  for(let x of arr) {
    console.log(x);
  }
  // 3
  // 5
  // 7

  for(let x of "abc") {
    console.log(x);
  }
  // a
  // b
  // c

forEach Method of Array

  let arr = [3, 5, 7];
  arr.forEach(function(value) {
    console.log(value);
    });

    // 3
    // 5
    // 7

Break and Continue

• break breaks innermost enclosing loop statement
• continue skips to next iteration of innermost enclosing loop statement

Labels

```javascript
thing: // this is the label
while(stuff) {
  // other stuff
}
```

- allows breaking or continuing out of outer loops
- does **not** allow `goto`, nor anything like it

Functions

'use strict';
function multiply(a, b) {
  return a * b;
}

multiply (5, 2); // 10

multiply(3, 5, 4); // 15, ignores everything else

multiply(5); // NaN

Facts

• No function overloading
• Functions are first class because they are objects
  • Functions can have properties
  • Functions can be passed as a parameter
  • Functions can be returned from other functions
  • JavaScript has higher order functions!

Extra Bits

False-y Values

• false
• null
• undefined
• 0
• NaN
• ""

Using typeof

this is an operator

console.log(typeof 'frog'); // string

console.log(typeof 12); // number