Arithmetic Operators

original slides

See the Pen 2.1 Arithmetic Operators by LSU DDEM (@lsuddem) on CodePen.

slides

Javascript Operators

  • Operators are used in programming to assign new values, compare values, test values, update values, perform arithmetic on values, etc.
  • In short, operators are used to manipulate variables in a number of ways.
  • So far, we’ve only really dealt with the default assignment operator, =, like when we say:
var usingAssignmentOperator = “the equals sign is the assignment operator”

In total, there are seven categories of operators in JavaScript.

These include operators for arithmetic operations, assignments, string operations, comparisons, logical operations, conditional operations, and other types of operators that are worth mentioning.

Arithmetic Operators

  • JavaScript’s arithmetic operators are used to perform arithmetic in your code. Arithmetic operators each have a symbol known as the operator that is used to perform the operation.

1. Addition : adding two values or variables together

  • Operator: +
  • Examples: let sum = 5 + 7000; let x, y; x = 20; y = 30; let z = x + y + 400;

  • Q : What is the value of variable z?

    2. Subtraction : subtracting one value or variable from another

  • Operator: -

  • Examples:

    let minus = 300 - 87;
let a, b;
a = 83;
b = 65;
let c =  a - b;

  • Q : What is the value of variable c?

    3. Multiplication : mutliplying multiple values or variables together

  • Operator: *

  • Examples:

    let product = 75 * 39;
let j, k;
j = 14;
k = 92;
let l = j * k * .5;

  • Q : What is the value of variable l?

    4. Division : dividing one or more values or variables by another

  • Operator: /

  • Examples:

    let quotient = 5016 / 6;
let q, w;
q = 46;
w = 138;
let p = (w / q) / 3; When there are multiple operations on a single line, the answer is calculated in the order of PEMDAS

    • Q : What is the value of variable p?

      5. Modulus : retrieving the remainder of one or more values or variables being divided by another

  • Operator: %

  • Examples:

    let modulus = 33%15; the value of modulus would be 3, because 32 goes into 15 twice, with 3 left over.
let h = 46;
let i = 13;
let g = h % i;

  • Q : What is the value of variable g?

    6. Increment : increasing the value of a variable by 1 (adding 1)

  • Operator: ++

  • Examples:

    let someValue = 10;
someValue++;
let newValue = someValue++;

  • Q : What is the value of the variable named newValue?

    7. Decrement : decreasing the value of a variable by 1 (subtracting 1)

  • Operator: –

  • Examples:

    let someOtherValue = 90;
someOtherValue--;
let anotherNewValue = someOtherValue--;

  • Q : What is the value of the variable named anotherNewValue?

  • The operators can be used on fixed values:

    let adding = 5 + 5;
let subtracting = 10 - 5;
let dividing = 40 / 5;
let multiplying = 80 * 3;
let modulos = 20 % 8;

  • On variables:

    Arithmetic operators can also be used on variables:
let number = 50;
let newAdding =  adding + number;
let newSubtracting = subtracting - number;
let newDividing = number / dividing;
let newMultiplying = multiplying * number;
let newModulos = number % modulos;

  • Or on a mix of both fixed values and variables:

    newAdding =  adding + 30;
newSubtracting = subtracting - 23;
newDividing = 5 / dividing;
newMultiplying = multiplying * 7;
newModulos = 24 % modulos;

    Note about the increment and decrement operators:

  • Increment and decrement can either go before or after the variable name, for example:

    myVar = 3;
myVar++ 
or
++myVar

  • When the increment operator happens after the variable, its the post-increment operator. If its before the variable, it’s the pre-increment operator.

    Here’s the different:

let myVar = 2
document.write(myVar++)
document.write(myVar++)
document.write(myVar++)
console.log(myVar)

let myVar1 = 2
document.write(++myVar)
document.write(++myVar)
document.write(++myVar)
console.log(myVar1)

  • The output of the first example is 234, because the document.write is executed before the value is updated. The variable is equal to 5 after the other operations.

  • The output of the second example is 345, because the document.write is executed after the value is updated. The variable is equal to 5 after the other operations.

    Exercise 2.1

See the Pen Untitled by LSU DDEM (@lsuddem) on CodePen.