# Aantekeningen tijdens een cursus
- **numbers** (e.g. 4, 10)
- **strings** (e.g. "dogs go woof!")
- **booleans** (e.g. true, false, 5 > 4)
- **console.log**() = printing outcome
- **condition** is tussen de ( )
- **syntax** = taal, termen.
- **Statement** = if (condition)
- **condition**
- **inputs**
- **function**
- **return** The return keyword simply gives the programmer back the value that comes out of the function.
- GlobalVar = Var outside a function
- Local Variable = var in a function
- Scope = bereik
```javascript
if (condition)
{
// if condition is true
// do this code
}
else // "otherwise"
{
// do this code instead
}
```
**Dingetjes**
- > Greater than
- < Less than
- <= Less than or equal to
- >= Greater than or equal to
- === Equal to
- !== Not equal to
- = vergelijken
- ( ): control order of operations (bij rek)
- * and /: multiplication and division
- - and +: subtraction and addition
- **Modulo**: When % is placed between two numbers, the computer will divide the first number by the second, and then return the remainder of that division. (13 % 7 evaluates to 6)
- Math.random() that variable will equal a number between 0 and 1.
**Modulo**
5%2 = 1 (oneven)
4%2 = 0 (even)
**Doeners**
- **confirm**("I am ok");
- **prompt**("Are you ok?”);
- **string length** (e.g. "Emily".length);
- //**comment**
- **console.log**
- **return**
- **for loop**
- **arrays**
VOORBEELD
console.log("Xiao Hui".length < 122);
console.log("Goody Donaldson".length > 8);
console.log(8*2 === 16);
alles is true
**Strings**
- **Substring**, deel van orginele volledige string
- ”laptop".substring(3,6); _From 4th to 6th letter of "laptop" uitkomst is top_
**Variabelen**
- declare: var varName = data;
- **Declare** a var is een var een naampje geven
- de var inzetten dmv =varName
- de var een functie (**function**) geven met {}
- console.log("Hey" + "you"); will print out Heyyou. That's not what we want!
- If you want a space between words, you must add that space as well!
- console.log("Hey" + " " + "you"); will print out Hey you
- This joining of strings is called **concatenation**
VOORBEELD VAR MAKEN + INZETTEN
```javascript
var myCountry = "string";
console.log(myCountry.length);
```
VOORBEELD FUNCTIO MAKEN
`var greetings = function ( _parameter_ ) { _reusable code_ }`
_Every line of code in this block { } must end with a ;._
_Functie oproepen:_ `greetings(“tekst”)`
VOORBEELD VAR MET FUNCTION
```javascript
var divideByThree = function (number) {
var val = number / 3;
console.log(val);
};
divideByThree(12);
```
VOORBEELD SUBSTRING
`console.log(myCountry.substring(0,3));`
**TIPS**
- The computer doesn't worry about extra spaces between words or brackets
- It just cares about the order of where things are placed and that you have used the right characters (){}[]"";
- For extra help, a program called a 'linter' is checking your code and will put a red 'x' next to the first line that contains errors
- At the end of each line of code (within the { }) and after the entire function (after the { }), please put a semi-colon. The semi-colon acts like a period in a sentence. It helps the computer know where there are stopping points in the code.
- D.R.Y.
**VOORBEELD**
```javascript
var myFinish = "I finished my first course!";
var myFail=“string fuck yout”
if (28 === 28)if
{
console.log(myFinish);
}
else
{
console.log(“myFail”);
}
```
VOORBEELD
```javascript
_declare function:_
var foodDemand = function (food)
_Herbruikbare code_
{
console.log("I want to eat" + " " + food);
};
_call:_
foodDemand("burrito's");
```
**VAR IN VAR**
```javascript
var orangeCost = function (price) {
var total = (price * 5);
console.log(total);
};
orangeCost(3);
```
Je koopt altijd 5 oranges. De prijs wisselt en kun je in veranderen bij de call
**RETURN VOORBEELD**
```javascript
_// Parameter is a number, and we do math with that parameter_
var timesTwo = function(number) {
return number * 2;
};
_// Call timesTwo here!_
var newNumber = (timesTwo(4));
console.log(newNumber);
```
**FOR LOOP**
```javascript
for (var i = 1; i < 11; i = i + 1) {
/* your code here */;
}
```
**LOOP regels**
**Rules to learn**
a. A more efficient way to code to increment up by 1 is to write i++.
b. We decrement down by 1 by writing i--.
c. We can increment up by any value by writing i += x, where x is how much we want to increment up by. e.g., i += 3 counts up by 3s.
d. We can decrement down by any value by writing i -= x. (See the Hint for more.)
e. Be **very** careful with your syntax—if you write a loop that can't properly end, it's called an **infinite loop**. It will crash your browser!
**ARRAYS**
```javascript
var names = ["Mao","Gandhi","Mandela"];
var sizes = [4, 6, 3, 2, 1, 9];
var mixed = [34, "candy", "blue", 11];
var arrayName = [data, data, data];
- Any time you see data surrounded by [ ], it is an array.
- the position (or the index) of each bit of data is counted starting from 0, not 1.
var junkData = ["Eddie Murphy", 49, "peanuts", 31];
console.log(junkData[3])
```