Expressions are units of code used to resolve a value just like in algebra.
1 + 1 = 2
In coding, expressions such use operators such as the = sign to assign values to variables:
x = 100.
In this example, the variable x is equal to 100.
In basic expressions, the order of precedence rule (PEMDAS) applies to the operators when evaluating:
P arentheses
E xponents
M inus
D ivision
A ddition
S ubtraction
Javascript has many different types of operators. Some of the most used are:
//Assignment Operators
x = y
x += y //equal to x = x + y
x -= y //equal to x = x - y
//Comparison Operators
== //Equals
!= //Not Equal
=== //Strict Equal
> //Greater than
<= //Less than or equal
//Arithmetic Operators
% //Remainder (modulo) 12%5 returns 2
++ //Increment by 1 (5++ returns 6)
-- //Decrement by 1 (5-- returns 4)
** //Exponentation (2 ** 3 returns 8)
//Logical Operators
&& //logical AND (expr1 && expr2, both have to be TRUE to return TRUE else FALSE)
|| //logical OR (expr1 || expr2, one expression has to be TRUE to return TRUE else FALSE)
! //logical NOT (!expr, returns FALSE if expr is TRUE, else TRUE)
Loops are an easy way to repeat a block of code based on a conditional or iterable statement. Here are a couple basic loops
for loops repeat until the condition specified evaluates to false. Basic syntax:
for(initialExpression; conditionalExpression; incrementExpression){
execute this code while conditionalExpression is true
}
//example, this will console log 5 times
for(let i = 0; i < 5; i++){
console.log(i)
}
while loops execute as long as the condition is true. Basic Syntax:
while(condition){
execute this code while condition is true
}
//example, this is an infinite loop and will log 'error' forever
while(true){
console.log('error')
}
There are many ways to combine operators and loops and many use cases for loops in creating web pages, applications and even games.
References: