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