01 / 05
A number is not wrapped in "
The basics of syntax
INPUT · Slides
Text and numbers are different things
02 / 05
Wrapped or bare, they are not the same
"42" and 42 look identical on the screen, but inside JS they are two different things.
"42"… text (we call it a string)42… a number
Same look, different handling. This is one of the first places people trip up.
console.log("42");console.log(42);Result
42 42
03 / 05
You see the difference when you do maths
A number can be worked out. A string cannot.
Wrap it in " and it stops being a sum — it becomes just some characters.
console.log(3 + 5);console.log("3 + 5");Result
8 3 + 5
04 / 05
A mistake people make
A phone number or a postcode looks like a number, but you normally hold it as a string.
As a number the leading 0 disappears, and you are never going to add it to anything anyway.
The question is not "does it look like digits" but "am I going to do maths with it".
console.log(0123);console.log("0123");Result
83 0123
05 / 05
How to decide
When you are not sure, think of it this way.
- Words for a person to read → a string (wrapped in
") - A number you will do maths with → a number (left bare)
These two come up again and again from here on. When you hunt down an error, the first thing you will check is "is this a string or a number".
Let us get the difference into your fingers.