wis-aerrajiy/LearnJsAdvance

the whole course is about javascript

    https://www.youtube.com/watch?v=-xL3LXBiGfw&list=PLknwEmKsW8OuTqUDaFRBiAViDZ5uI3VcE&index=2

1 : Window , document , console :

How browser work ? what is DOM : document object model :
control the browser from javascript
window : {
    location : {
        href : "https://www.google.com"
    },
    history : {
        back : function() {
            // go back
        },
        forward : function() {
            // go forward
        },
        ...
    },
    ...
}

control the page from javascript :

document : {
    html : {
        head : {
            title : "hello world"
        },
        body : {
            h1 : "hello world"
        }
    }
}

control the console from javascript :

console : {
    log : function() {
        // print to console
    },
    error : function() {
        // print to console
    },
    ...
}

javascript Data types :

dataType : {
    primitive : {
        string : "hello world",
        number : 123,
        boolean : true,
        null : null,
        undefined : undefined
    },
    nonPrimitive : {
        object : {
            name : "ahmed",
            age : 20
        },
        function : function() {
            // do something
        },
        array : [1,2,3,4,5],
    }
}


javascript variables : var , let , const

javascript conactenation :

var name = "ahmed";
var age = 20;
var result;
result = "my name is " + name + " and i am " + age; 
or :
result = `my name is ${name} and i am ${age}`;
console.log(result);

javascript operators :

+ , - , * , / , % , ++ , -- , += , -= , *= , /= , %= , == , === , != , !== , > , < , >= , <= , && , || , ! , ? , : , = , += , -= , *= , /= , %= , ** , **= , << , >> , >>> , &= , |= , ^= , &&= , ||= , ?? , ??= , =>
https://www.w3schools.com/js/js_operators.asp

+ : add
- : sub
* : mul
/ : div
% : mod
** : power
= : assign
== : equal
=== : equal and same type
!= : not equal
!== : not equal and not same type

javascript : cast data type :

auto cast to number : {
    var a = "10", b = "20";
    var x = a + b;   // 1020 | // type: string
    var y = +a + +b; // 30   | // type: number
    var z = a - b;   // -10  | // type: number

    var v = "ayman";
    +v // NaN => not a number
}

manual cast to number : {
    var a = "10";
    var x = Number(a);      // 30
    var y = parseInt(a);    // 30
    var z = parseFloat(a);  // 30
}

manual cast to string : {
    var a = 10;
    var x = String(a);      // "10"
    var y = a.toString();   // "10"
}

javascript : Objects Methods : {

    Number() : {
        Number.isInteger() : check if number is integer
        Number.isNaN() : check if number is NaN
        https://www.w3schools.com/js/js_number_methods.asp
    }

    Math() : {
        Math.abs() : absolute value
        Math.ceil() : round up
        Math.floor() : round down
        Math.round() : round to nearest
        Math.max() : return max number
        Math.min() : return min number
        Math.pow() : return power
        Math.sqrt() : return square root
        Math.random() : return random number
        https://www.w3schools.com/js/js_math.asp
    }
}