JavaScript Math Operators

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Math Operators

// Number + Number -> addition
1 + 2; // 3
 
// Boolean + Number -> addition
true + 1; // 2
 
// Boolean + Boolean -> addition
false + false; // 0
 
// String + String -> concatenation
"foo" + "bar"; // "foobar"
 
// Number + String -> concatenation
5 + "foo"; // "5foo"
 
// String + Boolean -> concatenation
"foo" + false; // "foofalse"
 
// Subtraction with numbers
5 - 3; // 2
3 - 5; // -2
 
// Number - String -> Subtraction
15 - "4"; // 11
 
// Subtraction with non-numbers
"foo" - 3; // NaN

Increment and Decrement

• If used postfix, with operator after operand (for example, x++), the increment operator increments and returns the value before incrementing.
• If used prefix, with operator before operand (for example, ++x), the increment operator increments and returns the value after incrementing.

// Prefix increment
let a = 2;
b = ++a;
// a = 3
// b = 3
 
// Postfix increment
let x = 3;
y = x++;
// y = 3
// x = 4
 
// Prefix decrement
let a = 2;
b = --a;
 
// a = 1
// b = 1
 
// Postfix decrement
let x = 3;
y = x--;
// y = 3
// x = 2