113 lines
3.6 KiB
Markdown
113 lines
3.6 KiB
Markdown
# Global Variables
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How to define and use global variables. #docs #data #language #variables
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### @parent js/language
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A variable is a place where you can store data so that you can use it later in your code. A *global* variable is accessible from every point in your code.
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### Block Editor
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In the Block Editor, all variables are global. See [Block Editor](/microbit/blocks/editor) for info on creating global variables in a Block Editor script. The following block is used to set (assign) global variable's value:
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The block below retrieves (gets) the current value of a global variable:
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### Touch Develop
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In Touch Develop variables are either [global](/microbit/js/data) or [local](/microbit/reference/variables/var). Variables have a name, a [type](/microbit/js/types), and value:
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* the *name* is how you'll refer to the variable
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* the *type* refers to the kind of value a variable can store
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* the *value* refers to what's stored in the variable
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[Global variables](/microbit/js/data) are variables that are available throughout your script. Unlike [local variables](/microbit/reference/variables/var), global variables are accessible across functions and in nested code blocks.
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### Create a global variable
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To create a new global variable:
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1. In the Touch Develop [editor](/microbit/js/editor), click `script` (to the right of the search box).
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2. Click `+` **add new**.
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3. Click `data->` **data** and then choose a [type](/microbit/js/types).
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4. Enter a name for your global variable and click **OK**.
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### Set and use a global variable
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To use a global variable that you've declared (using steps above):
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1. In the Touch Develop [editor](/microbit/js/editor), click `data-> ` **data** or `data->` + *variable name*.
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2. Click `:=` (assignment).
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2. Click on the right-side of `:=` and type or click what you want to store in the variable.
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Your code should look something like this:
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// global number variable
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```
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counter = 2
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```
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// global string variable
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```
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name2 = "Mike"
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```
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// global boolean variable
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```
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bool = true
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```
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(for info on creating image variables, see [Image](/microbit/reference/image/image))
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Once you've defined a variable and set it's initial value, use the variable's name whenever you need what's stored in the variable. For example, the following code gets the value stored in the global `counter` variable and shows it on the screen:
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```
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basic.showNumber(counter, 100)
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```
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To change the contents of a variable use the [assignment operator](/microbit/reference/variables/assign) `:=`. The following code increments `counter` by 10:
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```
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counter = counter + 10
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```
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### Promote, demote, and extract
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To **promote** a local variable to a global variable:
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* select the local variable name and click `promote to data`. The [var](/microbit/reference/variables/var) keyword changes to the data symbol `data->`.
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To **demote** a global variable to a local variable:
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* select the global variable name and click `demote to var`
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To **extract** the content of a global variable to a local variable:
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* select the global variable name and click `extract to var`
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### See your global variables
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To see a list of the global variables in your script:
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* click `script` (along the top) and scroll down to the **vars** heading
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### Lessons
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[counter](/microbit/lessons/counter), [rotation animation](/microbit/lessons/rotation-animation), [digital pet](/microbit/lessons/digital-pet), [offset image](/microbit/lessons/offset-image)
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### See also
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[local variables](/microbit/reference/variables/var), [types](/microbit/js/types), [assignment operator](/microbit/reference/variables/assign)
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