# For loop

Category:Control

## for loop

Category: Control

Executes a block of statements a certain number of times depending on the initialization expression, conditional expression, and increment expression.

Instead of typing a block of statements again and again, you can use a for loop around the block of statements. The most common usage of a for loop is simply to use it as a counting loop to execute a block of code a certain number of times.

### Examples

```// Draw 4 dots along a line.
for(var i=0; i<4; i++){
dot(5);
moveForward();
}
```

Example: Count Down Count down to zero from ten using a negative increment.

```// Count down to zero from 10.
for(var i=10; i>0; i--){
write(i) ;
}
write('Blast Off!');
```

Example: One Inch Draw 8 tic marks along a line.

```penUp();
turnLeft();
moveForward(100);
turnLeft(180);
penDown();
for(var i=0; i<7; i++){
ticMark();
moveForward();
}
ticMark();
penUp();
moveForward();

function ticMark() {
turnLeft();
moveForward(5);
turnLeft(180);
moveForward(5);
turnLeft();
}
```

Example: Rake Draw a rake ranging the angles from -45 to 45 by 5s.

```// Draw a rake ranging the angles from -45 to 45 by 5s.
for(var angle=-45; angle<=45; angle=angle+5){
turnTo(angle);
moveForward(100);
turnLeft(180);
moveForward(100);
}
turnTo(180);
moveForward(200);
```

Example: Flower Draw a flower with a parameter number of petals. Works best for petalCount between 5 and 10.

 ```// Draw a flower with a parameter number of petals. Works best for petalCount between 5 and 10. drawFlower(5); function drawFlower(petalCount) { penColor("pink"); penUp(); for(var i=0; i<360; i=i+(360/petalCount)){ turnTo(i); moveForward(360/petalCount); dot((2/3)*360/petalCount); moveForward(-360/petalCount); } penColor("blue"); dot(360/petalCount/2); } ``` Example: Random Die Rolls Simulate rolling a die using a random number from 1 to 6, and roll the die 10000 times to check if the expected roll is 3.5.

```// Simulate rolling a die using a random number from 1 to 6, and roll the die 10000 times to check if the expected roll is 3.5.
var sum = 0;
for (var i = 0; i < 10000; i++) {
sum = sum + randomNumber(1,6);
}
console.log(sum/10000);
```

### Syntax

```for (initialization; condition; increment) {
// block of statements
}
```

Here is a typical construct for loop used to count from 0 to 3 to execute the block of code 4 times:

`for(var i = 0; i < 4; i++)`

initialization `var i = 0;` is executed once, before anything else. Create an identifier named i and initialize it to 0.

condition `i < 4;` is checked before each iteration, to see if the block of statements should execute or not. If i is less than 4.

increment `i++` is executed after every iteration, after the block of statements is executed. Increase (increment) i by 1.

### Tips

• You do not need to use i in the for loop statement, you can use any declared and initialized identifier.
• You can start (initialization) and end (condition) the loop at any values.
• You can use any increment, positive or negative.
• Be careful not to code an infinite loop where the condition is never false.
• Be careful not to code a loop that never executes because the condition is never true.

Found a bug in the documentation? Let us know at documentation@code.org

## Syntax

```for(var i=0; i<4; i++){ //code }
```

Found a bug in the documentation? Let us know at documentation@code.org