01 . Into to javascrtipt
• Js is a plAnd it allows developers to add dynamic and interactive effects to any webpage.
• We also use it to manipulate the content or the CSS, load data from remote servers ,and really build entire applications in the browser,
• There has been a huge update to the language in 2015, which is officially called ES2015, but most people just call it ES6, |
Conditional operator
syntax: condition:true statement : false statement
const age = 88;
age >= 18 ? console.log("you can") :console.log("you wont ");
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Template literals
const firstname = "Sathiya";
const firstname1 = "SathiyaPriyan";
const $new = ${firstname} is a guy
;
console.log($new);
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Template literals - use varible in a string , use multiple line is easy
p1-use stright mode
"use strict";
-> Use certian things and visible errors
-> and like that write more secure code. And when secure, I mean that strict mode
makes it easier for us developers to avoid accidental error |
Array methods
// Adds
push - add an element in a end
unshift(): Adds elements to the beginning of an array.
//Remove
pop - remove last element of an array
shift(): Removes and returns the first element of an array.
//Find index
indexOf(): Returns the index of the first occurrence of a specified element ; minus value mean does not exit
//Check array exit or not
includes(): Checks if an array contains a specified element. - immutable |
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Link js file
<script src="index.js"></script>
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Link from another page , Script in same page simple use script tag
Type Conversion and Coercion
nan - not a valid number or not a number
Js - convert only string , boolen , number not other type |
True valuse and false value
5 falsy values in js
0,'',undefined , null , nan |
p2-Function declaration and expression
"use strict";
// Function declaration
function calAge1(birthYear) {
const age = 2029 - birthYear;
return age;
}
console.log(calAge1(2003));
// Anonymous function - expressions is a vaule
const me = function (birthYear) {
const age = 2029 - birthYear;
return age;
};
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Object
// and it's called the object literal Syntax
const spObject = {
firstName: "sathiya",
lastName: "sp",
age: 27,
destinitation: "student",
habits: ["productivity", "time management"],
};
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In arrays there is no way of giving these elements a name. And so we can't reference them by name, but only by their order number in which they appear in the array.
So we solve that problem we have another data structure in JavaScript, which is object
object is for unstructured data
array is for ordered data
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3 ways iof declaring a javascript
let , const is a modern way of declaring variable var is a old way of declarig of js
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let age = 0 // Varaibale declare
age = 1 // it is a mutated variable or reasign variable
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let vs const -> const is a best practice .
The reason for this is that it's a good practice
to have as little variable mutations or variable changes as possible because changing variables introduces a potential bug
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var is completely avoid
or declare nothing - bad practice |
Equality operator
The strict equality operator ( ===
) compares two values without type coercion
while the loose equality operator ( ==
) compares values with type coercion in JavaScript.is full of really weird rules and behaviors. this can introduce many hard
to find bugs into our code. clean code |
p3-Arrow functions
syntax : let func = (arg1, arg2, ..., argN) => expression
It is introuded in ES6 vesrion
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Javascript dot vs bracket
Put into any via loops
const yearsfa = [1991, 2007, 1967, 2020];
const age = [];
const newArray = [];
function calAge($var) {
return 2023 - $var;
}
for (let count = 0; count <= years.length; count++) {
console.log((age[count] = calAge(years[count])));
newArray.push(age);
}
console.log("--");
console.log(newArray);
console.log(calAge(2003));
for (let count = 0; count < array.length; count++) {
const element = array[count];
}
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To check what kind of data type
Data types
NULL is undefined data type
operator
Check c notes
Operator precedence So basically the order in which operators are executed. |
Get input from webpage
const $colour = prompt(`Tell your
most favourate colour`);
console.log($colour);
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Calling function inside another functions
function cutFruit(fruit) {
return fruit * 4;
}
function fruitProcessor(apples, oranges) {
const appleP = cutFruit(apples);
const orangesP = cutFruit(oranges);
const juice = Juice with ${apples} apples and ${oranges} oranges
;
return juice;
}
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