javascript.txt

>>>>>>>> JavaScript <<<<<<<<<


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Built-in Functions: 

splice(), map(), push()

map(), filter(), reduce(), some(), every(), includes(), slice(), splice().

‎map(), filter(), reduce(), slice()

eval(), parseInt(), parseFloat(), escape(), unscape(), 

write(), alert()

Object.create(),Object.create(),Object.keys(),Object.values(),Object.entries()
Object.freeze(),Object.seal();Object.getPrototypeOf()


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// Splice():
Syntax:
array.splice(index, howmany, item1, ....., itemX)
The splice() method adds and/or removes array elements.
The splice() method overwrites the original array.
Ex: anyArray.splice(index,1)
...............


>>>>> Javascript Predefined Functions <<<<<<<<<<


map(), filter(), reduce(), some(), every(), includes(), slice(), splice().

‎map(), filter(), reduce(), slice()

eval(), parseInt(), parseFloat(), escape(), unscape(), 

write(), alert()



1. Shorten the console log

const log = console.log.bind(document)
log("does it work?")
log("yes")
log(12)

2. Merge two arrays into one

 const array1 = ["one", "two", "three"]
 const array2 = ["four", "five", "six"]
 const merged = array1.concat(array2)

 console.log(merged) // "one", "two", "three", "four", "five", "six"

3. Merge two objects into one

 const User = {
    name: "ajay sisaudiya",
    gender: "Male"
 };

 const article = {
    title: "Javascript tips",
    data: '2022-06-01'
 };

 const summary = {...User, ...article}

 4. Shorten an array
 const array1 = ["One", "Two", "Three", "Four", "Five", "Six"]
 big_array.length = 3
 console.log(big_array)  //["One", "Two", "Three"]
 
 5. Shuffle an array
 const array1 = ["One", "Two", "Three", "Four", "Five", "Six"]
 array.sort(compareFn: function(){ return Math.random() - 0.5})
 console.log(array)

 6. Use isNum to verify a number

 console.log(isNum(n:1338))  //true
 console.log(isNum(n:13.38))  //true
 console.log(isNum(n:"Javascript"))  //false

 7. Use isStr to verify a string

 const isStr = value => typeof value === 'string';

 console.log(isStr(value:'JavaScript'));   //true
 console.log(isStr(value:346));           //false
 console.log(isStr(value:true));         //false

8. Use isNull

const isNull = value => value === null || value === undefinced;

console.log(isNull(value:null))     // true
console.log(isNull())              //  true
console.log(isNull(value:123))    //   false
console.log(isNull(value:"J"))   // false

9. Calculate the performance of a function

const start = performance.now();
//some program
const end = performance.now();
const total = start - end
console.log("function takes " + total + " milisecond");

10. Remove duplicates from an array

const delDuplicates = array => [...new Set(array)]
console.log(delDuplicates(array:["One", "Two", "Three", "Two", "Four",
                                 "Five", "Four", "Three", "One", "Five",
                                 "Five", "Three", "Four", "One", "Two"
                                 ]))

11. Use logical AND/OR for conditions

const input = 2 
input === 5 && console.log("it is 5")
input === 5 || console.log("it is not 5")

or for assigning values:

function defaultsTo5(arg){
  arg = arg || 5; arg will have 5 as a default value if not set
  console.log(arg)
}

let arg1 = 2
let arg2 = null
defaultsTo5(arg1) //2
defaultsTo5(arg2) //5


12. Ternary operator

function temperature(temp) {
  return (temp > 39 || temp < 35.5) ? 'Visit Doctor!'
    : (temp < 37.5 && temp > 36.5) ? 'Go Out and Play!!'
      : (temp <= 39 && temp >= 35.5) ? 'Take Some Rest!' : ''
}

console.log(temperature(temp:38))   // Take Some Rest!
console.log(temperature(temp:36))   // Take Some Rest!
console.log(temperature(temp:39.1)) // Visit Doctor!
console.log(temperature(temp:35.1)) // Visit Doctor!
console.log(temperature(temp:37))   // Go Out and Play



1.Spread operator
2.for…of iterator
3.includes()
4.some()
5.every()
6.filter()
7.map()
8.reduce()


1. Spread operator

const favouriteFood = ['Pizza', 'Fries', 'Swedish-meatballs'];
console.log(...favoriteFood);

//Pizza Fries Swedish-meatballs

2. for…of iterator

const toolBox = ['Hammer', 'Screwdriver', 'Ruler']

for(const item of toolBox){
  console.log(item)
}

//Hammer
//Screwdrive
//Ruler

3. Includes() method

const garage = ['BMW', 'AUDI', 'VOLVO'];
const findCar = garage.includes('BMW');

console.log(findCar)      // true

4. Some() method

ES5:

 const age = [15, 13, 17];
 age.some(function(person){
   return person >= 17
 })                              //true

ES6: 

 const age = [15, 13, 17];
 age.some((person) => person >= 17)    //true

5. Every() method

ES5: 

const age = [15, 20, 19];
   age.every(function(person){
    return person >= 18;
   })                           //Output: false


ES6: 

const age = [15, 20, 19];
age.every((person) => person >= 18); //Output: false

6. Filter() method

ES5: 

const prices = [25, 30, 15, 55, 40, 10];
prices.filter(function(){
  return price >= 30;
});                   //Output: [30, 55, 40]


ES6:

const prices = [25, 30, 15, 55, 40, 10];
prices.filter((price) => price >= 30)

// [30, 55, 40]


7. Map() method

ES5:

const productPriceList = [200, 350, 1500, 5000];
productPriceList.map(function(item){
  return item * 0.75;
});

// [150, 262.5, 1125, 3750]

ES6: 

const productPriceList = [200, 350, 1500, 5000];
productPriceList.map((item) => item * 0.75);

// [150, 262.5, 1125, 3750]


8. Reduce() method

ES5: 

const weeklyExpresses = [200, 350, 1500, 5000, 450, 680, 350]

weeklyExpensses.reduce(function(first, last){
  return first + last;
});

//8530

ES6: 

const weeklyExpresses = [200, 350, 1500, 5000, 450, 680, 350]

weeklyExpensses.reduce((first, last) => first + last);

//8530
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ES6: Object

//Details: Website Links
//https://www.digitalocean.com/community/tutorials/how-to-use-object-methods-in-javascript

--> Operations On Objects

Object.assign(obj,objnew);
Object.create(obj);
Object.keys(obj);
Object.values(obj);
Object.entries(obj);  
Object.freeze(obj);
Object.seal(obj)
Object.getPrototypeOf(obj)


Example 01:
----------- 
           //Object.create();

// Initialize an object with properties and methods
const job = {
    position: 'cashier',
    type: 'hourly',
    isAvailable: true,
    showDetails() {
        const accepting = this.isAvailable ? 'is accepting applications' : "is not currently accepting applications";

        console.log(`The ${this.position} position is ${this.type} and ${accepting}.`);
    }
};

// Use Object.create to pass properties
const barista = Object.create(job);

barista.position = "barista";
barista.showDetails();


Example 02: 
-----------
           //Object.keys()

// Initialize an object
const employees = {
  boss: 'Michael',
  secretary: 'Pam',
  sales: 'Jim',
  accountant: 'Oscar'
};

// Get the keys of the object
const keys = Object.keys(employees);

console.log(keys);


// Iterate through the keys
Object.keys(employees).forEach(key => {
    let value = employees[key];

   console.log(`${key}: ${value}`);
});


Example 03:
----------
              // Object.values()

// Initialize an object
const session = {
    id: 1,
    time: `26-July-2018`,
    device: 'mobile',
    browser: 'Chrome'
};

// Get all values of the object
const values = Object.values(session);

console.log(values);


Example 04: 
             // Object.entries()

// Initialize an object
const operatingSystem = {
    name: 'Ubuntu',
    version: 18.04,
    license: 'Open Source'
};

// Get the object key/value pairs
const entries = Object.entries(operatingSystem);

console.log(entries);


// Loop through the results
entries.forEach(entry => {
    let key = entry[0];
    let value = entry[1];

    console.log(`${key}: ${value}`);
});


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