Flash cards
Review the key moves
What is the main idea behind JavaScript Primitives?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
Which statement best captures the main point of this lesson?
Complete the missing token from the example code.
// Using double quotes: ___ carName1 = "Volvo XC60"; // Using single quotes: let carName2 = 'Volvo XC60';Put the learning moves in the order that makes the concept easiest to apply.
A JavaScript variable can hold 8 types of data.
7 Primitive types or an Object type.
JavaScript Strings
A string (or a text string) is a series of characters like "John Doe".
Strings are written with quotes. You can use single or double quotes:
Example
// Using double quotes: let carName1 = "Volvo XC60"; // Using single quotes: let carName2 = 'Volvo XC60';You can use quotes inside a string, as long as they don't match the quotes surrounding the string:
Example
// Single quote inside double quotes: let answer1 = "It's alright"; // Single quotes inside double quotes: let answer2 = "He is called 'Johnny'"; // Double quotes inside single quotes: let answer3 = 'He is called "Johnny"';Learn More
JavaScript String Methods
JavaScript String Search
JavaScript String Reference
JavaScript Numbers
All JavaScript numbers are stored as decimal numbers (floating point).
Numbers can be written with, or without decimals:
Example
// With decimals: let x1 = 34.00; // Without decimals: let x2 = 34;Exponential Notation
Extra large or extra small numbers can be written with scientific (exponential) notation:
Example
let y = 123e5; // 12300000
let z = 123e-5; // 0.00123Number Types
Most programming languages have many number types:
Whole numbers (integers): byte (8-bit), short (16-bit), int (32-bit), long (64-bit)
Real numbers (floating-point): float (32-bit), double (64-bit).
Javascript numbers are always double (64-bit floating point).
Learn More
JavaScript Number Methods
JavaScript Number Properties
JavaScript Number Reference
JavaScript BigInt
All JavaScript numbers are stored in a 64-bit floating-point format.
JavaScript BigInt is a new datatype ( ES2020 ) that can be used to store integer values that are too big to be represented by a normal JavaScript Number.
Example
let x = BigInt("123456789012345678901234567890");JavaScript Booleans
Booleans can only have two values: true or false .
Example
let x = 5;
let y = 5;
let z = 6;
(x == y)
// Returns true (x == z) // Returns falseBooleans are often used in conditional testing.
The typeof Operator
You can use the JavaScript typeof operator to find the type of a JavaScript variable.
The typeof operator returns the type of a variable or an expression:
typeof "" // Returns
"string"
typeof "John" // Returns
"string"
typeof "John Doe" // Returns
"string"typeof 0 // Returns
"number"
typeof 314 // Returns
"number"
typeof 3.14 // Returns
"number"
typeof (3) // Returns
"number"
typeof (3 + 4) // Returns
"number"Undefined
In JavaScript, a variable without a value, has the value undefined . The type is also undefined .
Example
let car; // Value is undefined, type is undefinedAny variable can be emptied, by setting the value to undefined . The type will also be undefined .
car = undefined; // Value is undefined, type is undefinedEmpty Values
An empty value has nothing to do with undefined .
An empty string has both a legal value and a type.
Example
let car = ""; // The value is
"", the typeof is "string"Datatype null
A function can return null or a variable can be assigned the null value:
Example
let carName = null;The typeof operator returns object for null.
This is a historical quirk in JavaScript and does not indicate that null is an object.
The strict equality operator (===) compares both the value and the type of the operands.
It returns true only if both the operands values and types are null .
The loose equality operator (==) also returns true for a null value, but it also returns true if the value is undefined .
Using == is not recommended when checking for null .