Code Examples JavaScript ebook
How to remove and update array items
const arr1 = [‘FIRST’,’Laurence’,’Svekis’,100,false];
const arr2 = [‘SECOND’,2332,true,’Hello’,’Svekis’,400,false];
const arr3 = arr1.concat(arr1,arr2);
const arr4 = arr1;
arr2.push(arr1);
console.log(arr2);
console.log(arr3);
Array.prototype.push.apply(arr1,arr2);
console.log(arr1);
arr2.push(‘NEW ITEM’);
arr1.push(‘Arr 1 New’);
//delete arr1[12];
//delete arr2[7];
//arr1.length = 0;
arr1.splice(12,1,’REMOVED’,’SECOND’);
arr2.splice(3);
console.log(arr1);
console.log(arr2);
console.log(arr3);
console.log(arr4);
Comparing Data Type and automatic conversion of Data Types
let a = [10];
let b = 10;
let c = “10”;
if(a == b) console.log(`${a} == ${b}`);
if(a == c) console.log(`${a} == ${c}`);
if(a === b) console.log(`${a} === ${b}`);
if(a === c) console.log(`${a} === ${c}`);
if(a != b) console.log(`${a} != ${b}`);
if(a != c) console.log(`${a} != ${c}`);
if(a !== b) console.log(`${a} !== ${b}`);
if(a !== c) console.log(`${a} !== ${c}`);
let d = [];
let e = 0;
let f = false;
let g = ”;
let h = null;
let i = undefined;
let j = NaN;
console.clear();
if(d == e) console.log(`D ${d} == ${e}`);
if(e == f) console.log(`E ${e} == ${f}`);
if(f == g) console.log(`F ${f} == ${g}`);
if(g == h) console.log(`G ${g} == ${h}`);
if(h == i) console.log(`H ${h} == ${i}`);
if(i == j) console.log(`I ${i} == ${j}`);
if(j == d) console.log(`J ${j} == ${d}`);
if(g == d) console.log(`GD ${g} == ${d}`);
if(f == h) console.log(`FH ${f} == ${h}`);
if(f == i) console.log(`FI ${f} == ${i}`);
if(f == j) console.log(`FJ ${f} == ${j}`);
console.clear();
if(!d) console.log(`D Yes ${d}`);
if(!e) console.log(`E Yes ${e}`);
if(!f) console.log(`F Yes ${f}`);
if(!g) console.log(`G Yes ${g}`);
if(!h) console.log(`H Yes ${h}`);
if(!i) console.log(`I Yes ${i}`);
if(!j) console.log(`J Yes ${j}`);
if(d === e) console.log(`D ${d} === ${e}`);
if(e === f) console.log(`E ${e} === ${f}`);
if(f === g) console.log(`F ${f} === ${g}`);
if(g === h) console.log(`G ${g} === ${h}`);
if(h === i) console.log(`H ${h} === ${i}`);
if(i === j) console.log(`I ${i} === ${j}`);
if(j === d) console.log(`J ${j} === ${d}`);
Object Construction with JavaScript
function FullName(firstName,lastName){
this.firstName = firstName;
this.lastName = lastName;
this.full = `${firstName} ${lastName}`;
}
const person1 = new FullName(“Laurence”,”Svekis”);
console.log(person1.full);
const person2 = new FullName(“John”,”Svekis”);
console.log(person2.full);
const person3 = new FullName(“Mike”,”Smith”);
console.log(person3.full);
let val = `${person1.firstName} ${person1.lastName}`;
console.log(val);
JavaScript Immediately invoked functions coding examples
(function(){
console.log(‘ready’);
})();
(()=>{
console.log(‘ready arrow’);
})();
((a=1,b=2,c=3)=>{
console.log(a,b,c);
const val = a * b * c;
console.log(val);
})(5,6,7);
Random Numbers and Random Array items
const arr = [];
const arr1 = [];
for(let i=0;i<10;i++){
const val = ran(0,1000);
arr.push(val.toString());
}
for(let i=0;i<20;i++){
const ind = Math.floor(Math.random()*arr.length);
const val = arr[ind];
console.log(ind,val);
}
function ran(min,max){
return Math.floor(Math.random()*(max-min+1))+min;
}
for(let i=1;arr1.push(i++)<50;);
console.log(arr1);
const arr2 = arr.sort();
const arr3 = arr.reverse();
arr.sort(()=>{
return Math.random() – 0.5;
});
console.log(arr[0]);
arr.sort(()=>{
return Math.random() – 0.5;
});
console.log(arr[0]);
String Whitespace Cleaner and Remover
String.prototype.cleaner = function(){
return this.replace(/\s+/g,’ ‘).trim();
}
const myStr1 = ” Hello World “;
console.log(myStr1.cleaner());
let val = myStr1;
val = trimMyString(val);
console.log(val);
document.querySelector(‘.output’).textContent = val;
function trimMyString(str){
let val = str.replace(/\s+/g,’ ‘).trim();
//val = str.trimLeft();
//val = str.trimRight();
return val;
}
JavaScript Logical Conditions
let val = 5;
val = 6;
if(val == 5) {fun1(1);}
if(val == 5) fun1(2);
val == 5 && fun1(3);
val == 5 || fun1(4);
if(val != 5) fun1(5);
fun1();
let val2;
val2 = val2 || 100;
console.log(val2);
function fun1(v=1){
v = v || 1;
console.log(`Hello ${v}`);
}
Array Map Examples
const arr1 = [1,5,7,8,23,342,2,3,4];
const arr2 = arr1.map((val,ind,arr)=>{
console.log(val,ind,arr);
return val * val;
})
const arr3 = arr1.map(val => val*val);
const arr4 = arr1.map(callbackFun);
function callbackFun(val){
return val * val;
}
console.log(arr1);
console.log(arr2);
console.log(arr3);
console.log(arr4);
Array Method Includes
const arr = [“Svekis”,”Laurence”,1000,20,300,true,323,”Svekis”];
const arr1 = arr.map(String);
console.log(arr1);
const myInput = document.querySelector(‘input’);
const btn = document.querySelector(‘button’);
const output = document.querySelector(‘.output’);
btn.addEventListener(‘click’,(e)=>{
const val = myInput.value;
const result = arr1.includes(val);
let message;
if(result){
message= `${result} is found in the array content`;
}else{
message = `${result} is NOT found`;
}
output.textContent = message;
console.log(result);
})
let val = arr.includes(“Svekis”);
console.log(val);
val = arr.includes(“Svekis”,-1);
console.log(val);
JavaScript Serialization and deserialization
const output = document.querySelector(‘.output’);
const arr1 = [“Svekis”,”Laurence”,1000,true];
const obj1 = {
first : “Laurence”,
last : “Svekis”,
id : 1000,
num : 55,
mes : “Hello”,
boo : false
};
output.textContent = arr1;
output.textContent = obj1;
console.log(arr1);
console.log(obj1);
let val = JSON.stringify(obj1)
val = JSON.stringify(arr1);
console.log(val);
output.textContent = val;
output.textContent += arr1;
console.clear();
val = JSON.stringify(obj1,rep);
function rep(key,value){
console.log(key,value);
if( typeof value === ‘number’){
return undefined;
}
return value;
}
output.textContent = val;
val = JSON.stringify(obj1,[‘num’,’first’]);
output.textContent = val;
val = JSON.stringify(obj1,null);
output.textContent = val;
console.log(val);
val = JSON.stringify(obj1,null,’ ‘);
output.textContent += val;
console.log(val);
const str1 = JSON.stringify(obj1,[‘num’,’first’]);
const str2 = JSON.stringify(arr1);
console.clear();
console.log(str1);
console.log(str2);
const ob1 = JSON.parse(str1);
const ob2 = JSON.parse(str2);
console.clear();
console.log(ob1);
console.log(ob2);
JavaScript Stringify LocalStorage
<!DOCTYPE html>
<html>
<head>
<title>JavaScript Course</title>
</head>
<body>
<input type=”text”>
<button>Check</button>
<div class=”output”>Output</div>
<script src=”code6.js”></script>
</body>
</html>
const str1 = “Laurence Svekis”;
const myObj = {
first : “Laurence”,
last : “Svekis”,
id : 100
};
const myInput = document.querySelector(‘input’);
const btn = document.querySelector(‘button’);
const output = document.querySelector(‘.output’);
document.addEventListener(‘DOMContentLoaded’,init);
btn.addEventListener(‘click’,btnClicker);
function btnClicker(){
const val = myInput.value;
if(val.length > 0){
let user = JSON.parse(localStorage.getItem(‘user’));
user.first = val;
console.log(user);
localStorage.setItem(‘user’,JSON.stringify(user));
}
}
function init(){
console.log(‘ready’);
output.innerHTML = ”;
let val = localStorage.getItem(‘user’);
let user = JSON.parse(val);
if(!user.first){
let storeObj = JSON.stringify(myObj);
localStorage.setItem(‘user’,storeObj);
}else{
output.textContent = `${user.first} ${user.last}`;
}
console.log(val);
}
JavaScript Every Method
const arr1 = [1,4,54,23,5,7,34,66,1000];
const arr2 = [“Svekis”,”a”,”World”,”He”];
const arr3 = [“Svekis”,”Laurence”,”Cat”,”Hello”,”a”,”World”];
let val = arr1.every((ele)=>{
console.log(ele);
return ele < 10;
})
val = arr1.every(callBackFun);
function callBackFun(ele,ind,arr){
console.log(`${ele} ${ind}`);
return ele < 1000;
}
console.log(val);
console.log(arr1.every(x => x < 10000));
console.log(arr1.every(x => x < 1000));
console.clear();
val = arr2.every((ele)=>{
console.log(ele);
return ele.length < 15;
})
console.log(val);
console.clear();
val = arr2.every((ele)=>{
console.log(ele);
return arr3.includes(ele);
})
console.log(val);
JavaScript Adding Numbers Array
const arr1 = [32,43,556,2,3,4,4345];
let total = 0;
for(let i=0;i<arr1.length;i++){
console.log(arr1[i],total);
total += arr1[i];
}
console.log(total);
/*
total = 0;
for(let i in arr1){
console.log(arr1[i],total);
total += arr1[i];
}
console.log(total);
*/
total = 0;
for(let i=0,len=arr1.length;i<len;i++){
console.log(arr1[i],total);
total += arr1[i];
}
console.log(total);