typeof 123
typeof 0.1
typeof "this is a string" // denoted by either "string value goes in here" or 'string value in here'
typeof 'this is also a string'
typeof ""
typeof true // either true of false
typeof false
typeof undefined // the only undefined value is undefined
// `typeof` doesn't work with `null` values for backwards compatability reasons.
typeof null
// when checking if something's explicitly `null`, make sure to use null === null
typeof Symbol.iterator
6 + 3 // addition
6 - 3 // subtraction
6 * 3 // multiplication
6 / 3 // division
10 % 3 // If you divide 10 by 3, you get 3 and a remainder of 1
3 > 2 // 3 is greater than 2
3 < 2 // 3 is not less than 2 so this "outputs" or "returns" false
3 >= 3 // 3 is greater than or equal to 3
3 <= 4 // 3 is less than or equal to 4
3 == 3 // 3 is equal to 3
3 === 3 // 3 is equal to 3
3 == 2 // 3 isn't equal to 2 so this outputs or "returns" false
3 === 2 // 3 isn't equal to 2 so this outputs or "returns" false
3 != 2 // 3 isn't equal to 2
3 != 3 // 3 is equal to 3 so this outputs or "returns" false
3 !== 2 // 3 isn't equal to 2
"Hello" + " " + "World"
"444" + "-" + "444" + "-" + "4444"
true && true // the and operator outputs or "returns" true if both booleans given are true
true && false
false && false
true || false // the "or" operator returns true if at least one of the booleans given is true
true || true
false || false
!false // the negation operator "!" will flip the boolean value that comes after it.
// the opposite of false is true
!true // the opposite of true is false
num1 + num2
firstName + " " + lastName
true + true
+null == 0
"3" + 1
"3" - - 1
1 + + "3"
false == ""
!""
!!0 // 0 is falsy
!!null // null is falsy
!!undefined // undefined is falsey
!!"" // an empty string is falsy
!!123 // numbers other than 0 are truthy
!!"this is a string" // non-empty strings are truthy
"" == false
0 == false
"foobar" == true
"1" == 1
0 == "0"
undefined == null
"" === false
0 === false
"foobar" === true
"1" === 1
0 === "0"
undefined === null
{
// Like so:
return "this is my answer"
// This allows the value to be printed in this notebook.
// This isn't a JavaScript feature but rather a quirk of this website.
}
{
// Your Code Here
}
{
// Your Code Here
}
{
// Your Code Here
}
{
// Your Code Here
}
{
// Your code here
}
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Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
