pxt-calliope/docs/reference/js/string-functions.md
2016-04-01 16:22:47 -07:00

4.2 KiB

String Functions

string-related functions.

@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 to see the following string functions:

/* placeholder */

~hide

let str = "hi"

~

equals

find out if two strings are the same

Syntax

String -> equals (other : String) returns Boolean

Parameters

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 -> at (index: Number) returns String

Parameters

  • index- 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 -> concat (other : String) returns String

Parameters

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 -> count returns 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 -> substring (start : Number, length : Number) returns String

Parameters

  • start - Number; the starting character number (0 is the first character number in a string)
  • length - 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 -> to character code returns 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 -> to number returns Number

Example

The following code converts str into a number and stores it in x:

x = parseFloat(str)

See also

string, number, show string