JavaScript for WordPress (Crash Note)

*Developer choice
https://insights.stackoverflow.com/survey/2019#technology-_-programming-scripting-and-markup-languages

1.  With creating a JS file/ external file load (cache advantage – best way)
2.  Embed in HTML file with script tag – in header or footer area
3.  In HTML tag attributes – basically even related
    
    

Live JavaScript 4 Output Method Code

<script>

window.alert('Your content');
alert('Your content');
// this two thing working same

document.write('Your content');
// we can rewrite total document with this function - rewrite can be check by *
// use for testing only

document.getElementById('html-tag-id').innerHTML = "Your content";
// we can push content, or modify html content

console.log('Your content');
// we can show output in browser console
// use for debugging


</script>

Rewrite with document.write

document.addEventListener("DOMContentLoaded", function(){
    //it's will be load after full document loaded once
    document.write('Your content');
});

Output access method

1. window.print()
2. print()

<!-- Both are for printing -->
<button id="abc" onclick="window.print()">Print</button> 
<button id="abc" onclick="print()">Print</button>

• JavaScript Ignore Multiple Space
• JavaScript case sensitive

Some Quick Point

• Statement – Statement is the single line of instruction in a program.
• JavaScript can not count more than one space.

JavaScript Comment

• A single line can be commented by / (slash)
• Multiple lines can be commented by this format /* multiple lines */

User Input Function

prompt(‘instruction’)

Variable in JavaScript

What is variable ?
Variable is used storing data in a programming language.

We can define a variable in three different ways in JS. This is:

1. var
2. let
3. const

With this 3 ways, we can declare a variable.

var example

var a = 10 ;
var b;
var b = 10;

let example

let was came in ES6

let can’t be redeclared
example:

<script>
        let a = 5;
        let a = 10;
        document.write(a);
</script>
//uncaught SyntaxError: Identifier 'a' has already been declared

let have block scope facility

<script>
    if(true){
        let x = 5;
        console.log(x);//it's will show output
    }
    console.log(x);// it's will show a error
    //cause it's in different block
</script>

let can not be hoisted

const example

const can not be redeclared and reassigned, it’s also not possible to declare const variable without defining it.

<script>
    const a = 5;
    //const a - wrong
    //const a; a = 5; - wrong
</script>

JavaScript Operator

There are few type operator in JavaScript

• Assignment operators
• Comparison operators
• Arithmetic operators
• Bitwise operators
• Logical operators
• String operators
• Conditional (ternary) operator
• Comma operator
• Unary operators
• Relational operators

jQuery Syntax for WordPress

(function($){

})
(jQuery)