JAVASCRIPT BASICS

• Datatypes
• Values
• Variables
• Conditions
• Operators
• Loops
• Functions

HISTORY OF JAVASCRIPT

Initially, developers wanted something which could bring functionality to the browser; a scripting Language.

Code written could only be supportable in the browser from which it was written. Therefore, to come up with a solution for this, they came up with ECMA Script. ECMA script was a set of rules to be followed while coding in a browser. This wasn't compatible though, and ES6 was introduced. ES6 was a modified set of rules or instructions to govern coding in the browsers. Mocha(1995) to LiveScript (1996) to JavaScript (till date).Browsers during those back days only supported CSS and HTML only.

There were only 2 browsers in the ancient days, that is to say; internet Explorer and Netscape browser.

The JavaScript Basics

1.Dataypes(values)

Forexample:1.number(whole number and decimal number) such as 1, 6.4; 2.string forexample "leya".

• These have a single value.

arrays

• Here we have index and the value. To access any value. We use the help of index.

Objects
We have key and value.

• Forexample: Fname:Mackline, lname:leya

Objects have more than one value. Here you get power to create your own key for any value you be having yet in arrays you will always use index which is always constant and can't be changed.

• Forexample;let bankaccount ={fname:'leya',
  lname:'Mackline',
  mobileno:989372,
  };
  Console.log(numbers);
  Console.log (numbers.lname);

• Therefore, to access a particular object, we can use a dot symbol in between the objects.

2.Variables
Incase we want to store some of our values, we can use variables. Variables are folders or placeholder for a value.

Three different ways to declare a variable.

• 1.var x = 50; We should minimumly use var due to memory convenience.
• 2.let y = 50; *We can use it for changing values such as account balance ...

• 3.const z = 'leya';we use const when we don't want to change the value of that variable.
  Forexample:

  A var z to store a bank account number since it is a constant one.Incase we want to print something on the screen, we then use the statement below in the terminal; console.log(object);

• That is to say; console.log(fname) ;We can also use template literal.That is to say;
  console.log(my current first name is ${fname});

3.Operators
These come in when we are going to do some calculations. That is to say, calculations.

Examples of operators

• 1.assignment operators [=]
• 2.arithmetic operators [ , ×, ÷, %]
• 3.comparison operators [>, <, >=, <=, == which compares only values and ==== which compares both value and datatype Forexample; x=5; y='5';console.log(x==y) is true yet console.log(x===y) is false].

PICKUPS;

const accno;accno = "45689943";

This would bring an error because accno being a constant should be initialized on declaration.
Also; const accno = 4694647855 ;
accno = 1345950;
This would also output an error in the output because accno being a constant is initialized once and for all.

4.Decisions
These are also called conditions. We can use :
a) If else statements: here the statement in else is executed if all other statements in if and else, if blocks are not true.

b) Switch case

Here the default works like the else as in in if else conditional statements. We also use break in the switch cases when we have to go out of the switch case loop.

NB:

• Both if else and switch case statements do the same work, but if else is commonly used.

c) Ternary operators/, operations

These can be done by the use of only 2 operators, that is to say, ? and the ;. Anything written after the (?) is true and whatever is written after colon is false , and everything before the ? is a condition.That is to say; condition ? true ; false.

5.Loops

These can help in iteration of something such as a variable like array, to its end.

Some are examples of loops we have

i) do while loop:Here, atleast one statement is executed in the do block as an output. This is because the condition in such a loop is written at the end of the loop.
let a=5;
do{
console.log('The value of a is;', a);
a ;
}while(a<=4);

ii) while loop;Here, there can be also no statement executed as long as the condition is not true.

For example:
Let a = 6;
while(a<=4){
Console. log('value of a is: ', a );
a ;
}

iii) for loop

For example;for(let a=0; a<=5; a ){
Console. log('The value for a is:', a);
}

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