Type Conversion

Every value in our programs has a type. "7" is a string and 7 is a number. They might look almost identical, but Jiki treats them very differently. You can't add the string "7" to the number 3 and expect to get 10, because one of them is a piece of text and the other is a quantity.

Quite often we need to move a value from one type to another. This is called type conversion, and there are two conversions you'll reach for all the time.

Turning a string into a number

When you read characters out of a string, each character is itself a string, even when it looks like a digit. Before you can do any arithmetic with it, you need to turn it into a real number. We do that with Number().

Number("7")
// 7

Number("42")
// 42

Once you have an actual number, you can add it, multiply it, and everything else.

let digit = Number("7")
let doubled = digit * 2
// 14

If you hand Number() something that isn't a valid number, like Number("cat"), you won't get a number back at all, so it's worth making sure you only give it strings that really are digits.

Turning a number into a string

The opposite direction is just as handy. Sometimes you have a number and you want to treat it as text, maybe to join it onto another string or to look at its individual digits. We do that with String(), the mirror image of Number().

String(42)
// "42"

let count = 7
String(count)
// "7"

Now that it's a string, you can use all the usual string tools on it, like reading it character by character or checking its length.