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.