88 lines
2.3 KiB
Markdown
88 lines
2.3 KiB
Markdown
# Local Variables
|
|
|
|
How to define and use local variables.
|
|
|
|
### @parent language
|
|
|
|
A variable is a place where you can store and retrieve data. Variables have a name, a [type](/reference/types), and value:
|
|
|
|
* *name* is how you'll refer to the variable
|
|
* *type* refers to the kind of data a variable can store
|
|
* *value* refers to what's stored in the variable
|
|
|
|
### Var statement
|
|
|
|
Use the Block Editor variable statement to create a variable
|
|
and the [assignment operator](/blocks/variables/assign)
|
|
to store something in the variable.
|
|
|
|
For example, this code stores the number `2` in the `x` variable:
|
|
|
|
```blocks
|
|
let x = 2;
|
|
```
|
|
Here's how to define a variable in the Block Editor:
|
|
|
|
1. Click `variables`.
|
|
|
|
2. Change the default variable name if you like.
|
|
|
|
3. Drag a block type on the right-side of the [assignment operator](/blocks/variables/assign) and click the down arrow to change the variable name.
|
|
|
|
A variable is created for the number returned by the [brightness](/reference/led/brightness) function.
|
|
|
|
```blocks
|
|
let b = led.brightness();
|
|
```
|
|
|
|
### Using variables
|
|
|
|
Once you've defined a variable, just use the variable's name whenever you need what's stored in the variable. For example, the following code shows the value stored in `counter` on the LED screen:
|
|
|
|
```blocks
|
|
let counter = 1;
|
|
basic.showNumber(counter);
|
|
```
|
|
|
|
To change the contents of a variable use the assignment operator. The following code sets `counter` to 1 and then increments `counter` by 10:
|
|
|
|
```blocks
|
|
let counter = 1;
|
|
counter = counter + 10;
|
|
basic.showNumber(counter);
|
|
```
|
|
|
|
### Why use variables?
|
|
|
|
If you want to remember and modify data, you'll need a variable.
|
|
A counter is a great example:
|
|
|
|
```blocks
|
|
let counter = 0;
|
|
input.onButtonPressed(Button.A, () => {
|
|
counter = counter + 1;
|
|
basic.showNumber(counter);
|
|
});
|
|
```
|
|
|
|
### Local variables
|
|
|
|
Local variables exist only within the function or block of code where they're defined. For example:
|
|
|
|
```blocks
|
|
// x does NOT exist here.
|
|
if (led.brightness() > 128) {
|
|
// x exists here
|
|
let x = 0;
|
|
}
|
|
```
|
|
|
|
#### Notes
|
|
|
|
* You can use the default variable names if you'd like, however, it's best to use descriptive variable names. To change a variable name in the editor, select the down arrow next to the variable and then click "new variable".
|
|
|
|
### See also
|
|
|
|
[types](/reference/types), [assignment operator](/blocks/variables/assign)
|
|
|