Java script 1 — Variables & Identifiers
I want to share an incident of my neighbours. I give fruits to them since I don’t have any fridge at my home. My neighbour women names are Siri, Esha, Madi.
Siri is type of lady where whatever she takes first she will return that item only, she won’t take other items. Esha and Madi are not like Siri, they will return the exact things which we give and they will take other items also.
In the same way in java script we can store values in three ways using let, var, const
const is like Siri.
let, var are like Esha and Madi.
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Let’s go with the simple examples,
const location = “India”
console.log(variable); //output is “India”
const location = “America”
console.log(variable); // We will get error as shown bellow
let greet= “Hello world”
greet= “Hello”
console.log(greet); // out put is “Hello”
var direction = “right”
direction = “left”
console.log(direction); // out put is “left”
Variables NAMING convention.
We follow four rules where we call these rules as identifiers.
- Unique valriable name: Variable’s name should be unique.
If we give duplicate name we will get the error as shown below.
const variableName = “Hii”;
const variableName = “Hello”;
console.log(variableName);
2. No Reserved Keywords: For variable declaration we should not use reserved words(eg: let, const, var, function).In the following chapters we will learn reserved keywords in java script
const let = “Hii”;
3. First letter should be a letter or _ or $: If we assign any other signs it will throw the below error.
const *name = “Siri”
4. Remaining letters in a variable name should contain only letters or _ or $, otherwise you will get the below error:
const name_of_the_student = “Siri” // valid declaration
const name$ = “Siri” // valid declaration
const name* = “Siri” // invalid declaration
