JavaScript Fundamentals

Hey Guys,

Today we will start with the basic building blocks of every programming language, specifically in JavaScript.

Logical Operators

The logical operators are used to get boolean results by comparing the operands.

||     -     OR
&&   -    AND
!       -    NOT
??     -    Nullish coalescing

Precedence of AND < OR

|| - OR

• Evaluates operand from left to right.
• For each operand converts it to boolean. If its true stops and returns the original value
• If all the operand returned is false then returns the last operand.

&& - AND

AND is the reciprocate of OR. It returns the first false operand.

! - NOT

NOT is the opposite of its operand.

console.log(!true); // returns false

?? - Nullish Coalescing

It returns the first defined value which is not null or undefined.

Different between ?? and ||

• || returns the first truthy value
• ?? returns the first defined value
• Both || and ?? has same precedence
• While using ?? with other logical operators braces is must

Loops

• When we want to execute same code n number of times there comes the loops. It will execute the statement n no of times with the help of conditions.
• Some of the loops present in JavaScript

while(condition){
//loop body
}
---------------------------------------------------
for (initialize ; condition ; stepup ){
//loop body
}

----------------------------------------------------
do {
//loop body
} while (condition)
-----------------------------------------------------
switch(x)

case value 1:
//statement
break;
case value 2:
//statement

break;
.
.
.
default:
//statement
break;

• Above are the major loops present in loops.
• We can also nest loops to get our desired results.
• Break is used to break out of loop.
• continue is used to skip the current iteration(If a loop runs 10 times it has 10 iterations ) of loop.
• We can use label to access any loop in the nested loops.
• In switch statement we can group cases and comparison is strict equals.

Functions

• In programming we have a principle Never repeat
• Functions are used for that. If have a few lines of code which you would use few places in your program then functions comes in to picture.

  function func_Name(){
  //code
  }
  

• We have functions to do some task or give some value. To give some value we use return statements.
• We have parameters to functions and arguments which are passed to those parameters.

function sum(a,b){
return a+b;
}

sum(a,b); // here a, b are arguments

Function Expressions

Functions expression just an extension to functions does the same thing but the syntax is different.

Normal function 

function sum(a,b)
{
return a+b;
}

Function expressions

let sum=function(a,b)
{ 
return a+b
};

JavaScript function is a value here.

Callback

We can pass a function as a argument to another function it is called callback. We can also not name the function and use it as Anonymous functions.

function SumAndAvg(a,b,c){
let sum= a+b;
let Avg= avg(sum);
return Avg;
}
function avg(sum){
return sum/2;
}
SumAndAvg(1,2,avg); // Here we are avg is used as callback

Arrow Functions

It is same as function expressions but concise.

let sum=(a,b) => a+b;

Resources

• https://javascript.info/

• https://developer.mozilla.org/en-US/docs/Web/JavaScript

• https://eloquentjavascript.net/