Lesson 3 of 11
Four kinds of value, and why the quotes matter
Show on a big screen12 is a number. "12" looks the same but is not. Quote marks make it text.
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Step 1 of 3
- Four kinds, one value each: 12, "12", true, null.
- 12 and "12" look alike on the page.
- They are two different kinds.
The rule
The kind of a value is what the machine holds. It is not how the writing looks. Run it and ask: number, text, true or false, or nothing?
| The kind | Written down |
|---|---|
| number | 12 |
| text | "12" |
| true or false | true |
| nothing | null |
4.5 is a number too. Whole numbers and numbers with a decimal point are one kind here. The sign / divides, so 12 / 8 gives 1.5.
Quotes change the answer. 12 + 8 adds two numbers and gives 20. "12" + 8 joins the two as text and gives "128".
0 is a number. "" is text with no characters. false is a true or false value, not nothing. In this editor, only null means no value at all.
print writes something out. It gives back nothing.
Try the lab to finish this lesson.