JavaScript tutorial for beginners

JavaScript tutorial for beginners

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created by: websitemaking122

introduction to JavaScript

Q: what is JavaScript ?

A: JavaScript is a programming language for make webpage is interactive

Q: who create JavaScript language ?

A: brendan eich

JavaScript syntax

document.write("hello world");
alert("hello world");

explanation:

every statements separated by semicolon, NOTE: the statement separator is not required but very recommended
statement contains variables, expressions, and keywords
list of output methods:

methods	description
`alert()`	show an alert box
`document.write()`	write text on document
`console.log()`	write text on console

the structure of JavaScript comment is:

// this is a comment

JavaScript variable

step 1, use var keyword to declare variable

var text = "hello world";

step 2, output variable

document.write(myText);

when two statements are joined, it becomes:

var text = "hello world";
document.write(myText);

JavaScript function

step 1, use function keyword to declare function

function showText() {

}

step 2, write statement on function body

function showText() {
  document.write("hello world");
}

step 3, call function

function showText() {
  document.write("hello world");
}

showText();

JavaScript conditional

if - else

if(condition) {
  statements (it executed when is true);
} else {
  statements (it executed when is false);
}

if(15 > 10) {
  alert("true");
} else {
  alert("false");
}

switch - case - default

switch(expression) {
  case value:
    statements;
  break;
  ...
  default:
    statements;
}

switch("one") {
  case "one":
    alert("the number is one");
  break;
  case "two":
    alert("the number is two");
  break;
  default:
    alert("i don't understand");
}

JavaScript loop

for

for(initializing; condition; increment) {
  statements;
}

var i;

for(i = 0; i < 3; i++) {
  document.write("hello world" + "<br>");
}

while

while(condition) {
  statements;
}

var i = 0;

while(i < 3) {
  document.write("hello world" + "<br>");
  i++;
}

JavaScript operators

arichmetic operators = + - * /

comparison operators = > < == !=

logical operators = && || !