179 lines
4.2 KiB
Markdown
179 lines
4.2 KiB
Markdown
# String Functions
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string-related functions.
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### @parent js/language
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The following string related functions are available in Touch Develop for the BBC micro:bit:
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* **equals** - find out if two strings are the same
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* **at** - get a character within a string
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* **concat** - combine two strings
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* **count** - get the number of characters in a string
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* **substring** - get a portion of a string
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* **to character code** - converts a character into a character code
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* **to number** - converts a string into a number
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Select a string variable in the [Touch Develop editor](/microbit/js/editor) to see the following string functions:
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```
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/* placeholder */
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```
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### ~hide
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```
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let str = "hi"
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```
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### ~
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### equals
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find out if two strings are the same
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#### Syntax
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[String](/microbit/reference/types/string) `->` **equals** (other : [String](/microbit/reference/types/string)) *returns* [Boolean](/microbit/reference/types/boolean)
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#### Parameters
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* other - [String](/microbit/reference/types/string); a string
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#### Example
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the following code does something if `str` = "Hi":
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```
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if (str == "Hi") {
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// add code to do something here
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}
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```
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### at
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get a character within a string, using the specified index
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#### Syntax
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[String](/microbit/reference/types/string) `->` **at** (index: [Number](/microbit/reference/types/number)) *returns* [String](/microbit/reference/types/string)
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#### Parameters
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* index- [Number](/microbit/reference/types/number); the character number within a string (0 returns the first character)
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#### Example
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The following code gets the first character from the `str` string and stores it in the `first char` variable:
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```
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let firstChar = str[0]
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```
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### The `||` operator
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To combine two strings you can use the string concatenation operation `||` as shown below:
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```
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let s = "abc" + "def"
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let evaluatesToTrue = s == "abcdef"
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```
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NOTE: position the cursor outside of the string quotes, right after the string, for the || operator to appear in the keyboard.
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### concat
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combine two strings; like the concat operator (`||`)
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#### Syntax
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[String](/microbit/reference/types/string) `->` **concat** (other : [String](/microbit/reference/types/string)) *returns* [String](/microbit/reference/types/string)
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#### Parameters
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* other- [String](/microbit/reference/types/string); a string
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#### Example
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The following code combines two strings and displays the string on screen:
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```
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str = "Hi "
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str = str.concat("there")
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basic.showString(str, 100)
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```
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### count
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get the number of characters in a string
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#### Syntax
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[String](/microbit/reference/types/string) `->` **count** *returns* [Number](/microbit/reference/types/number)
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#### Example
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The following example gets the length of the `str` variable and stores it in the `x` variable:
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```
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let x = str.length
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```
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### Substring
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get a portion of a string, using a starting point and length
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#### Syntax
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[String](/microbit/reference/types/string) `->` **substring** (start : [Number](/microbit/reference/types/number), length : [Number](/microbit/reference/types/number)) *returns* [String](/microbit/reference/types/string)
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#### Parameters
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* start - [Number](/microbit/reference/types/number); the starting character number (0 is the first character number in a string)
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* length - [Number](/microbit/reference/types/number); the string length
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#### Example
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The following code gets characters 6, 7, and 8 from the `str` string:
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```
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let asubstring = str.substr(5, 3)
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```
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### to character code
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converts the first character of a string into a character code number (unicode)
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#### Syntax
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[String](/microbit/reference/types/string) `->` **to character code** *returns* [Number](/microbit/reference/types/number)
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#### Example
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The following code converts the first character of `str` into a character code and stores the code in `x`:
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```
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x = str.toCharacterCode()
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```
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### to number
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converts a string into a number
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#### Syntax
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[String](/microbit/reference/types/string) `->` **to number** *returns* [Number](/microbit/reference/types/number)
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#### Example
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The following code converts `str` into a number and stores it in `x`:
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```
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x = parseFloat(str)
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```
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### See also
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[string](/microbit/reference/types/string), [number](/microbit/reference/types/number), [show string](/microbit/reference/basic/show-string)
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