JS Primitives, Variables, and Operators

js-primitives.md

Primitives

• String
• Number
• Boolean
• Undefined
• Null

Variables

Variables can't start w/ numbers or special characters except _ and $.

Creating variables

var year; // initialized w/o value (undefined)
var year = 2011; // initialized and set (defined)

• var is not required when setting variables but is a best practice.
• variables are case-sensitive

create multiple variables w/ comma separation

var year, month, day; 
var year=2011, month=10, day=31;

Operators

Standard operators

• Equal == or ===

== does type coercion (conversion) before checking for equality; and === does strict equation which requires values to have the same type as well.

0 == false          // true
0 === false         // false, because they have different types (int, bool)
1 == "1"            // true
1 === "1"           // false, because they have different types (int, string)
null == undefined   // true
null === undefined  // false

• Or ||

• And &&

• Not !

• GT >

• LT <

• Modulo % returns the remainder of one number divided by another. e.g., 14 % 3 === 2

It's useful to test divisibility. The result of 0 indicates perfect divisibility.

Ternary Operators

Ternary operators are used as conditional shortcuts. The syntax is: condition ? result1 : result2;

The following examples are equivalent.

result = x > y ? 'good job' : 20;

if (x > y) {
  result = 'good job';
} else {
  result = 20;
}