Detailed explanation of basic syntax and data types of JavaScript

<script>
	alert("hello world");
</script>

<script src="js/abc.js"></script>

<script>
    var num = 1;
    alert(num);
</script>

if (2>1)
{
    alert("true");
}

<script>
    var score = 65;
    // alert(num);
    if (score>60&&score<70)
    {
        alert("60-70")
    }
    else if (score>70&&score<80)
    {
        alert(70-80)
    }
    else
    {
        alert("other")
    }
</script>

123 //Integer 123
123.1 //Floating point number 123.1
1.122e3 //Scientific notation NaN //not a number
Infinity //Infinity

'a' "abc"

\'
\n //line break\t //space\u4e2d //unicode encoding\x41 //ascii

var str = `haha
        nihao
        666`

let name='xay';
let words = `Hello, ${name}`;

word.length

word.toUpperCase()
word.toLowerCase()

substring(1) // extract from the first string to the last substring(1,3) //[1,3)

true false

&& //and| //or! //not

=
== // Different types, same value is true === // Absolutely equal, both type and value must be the same

<script>
    var arr = [1,2,3,4,5,'hello']
</script>

var person = {
    name: 'xay',
    age: 18,
    tags: ['js','java','python']
}

if (2>1)
{
    alert("true");
}

<script>
    var score = 65;
    // alert(num);
    if (score>60&&score<70)
    {
        alert("60-70")
    }
    else if (score>70&&score<80)
    {
        alert(70-80)
    }
    else
    {
        alert("other")
    }
</script>

age=0;
while (age<100)
{
    age+=1;
    console.log(age);
}

for (let i = 0; i < 5; i++) {
    console.log(i);
}

var arr = [1,2,3,4,5,6,7,8,9,10];
for (var num in arr)
{
    console.log(num)
}

var map = new Map([['tom',100],['jack',90],['haha',80]]);
var name=map.get('tom'); //Get value through key
console.log(name)

map.set('admin',10);
map.delete('tom') //deletion in map 

var set = new Set([3,1,1,1,1]);

set.add(2) //Add set.delete(1) //Delete console.log(set.has(3)); //Is there 3?

var map = new Map([['tom',100],['jack',90],['haha',80]]);
for (let x of map)
{
    console.log(x);
}

var set = new Set([3,1,1,1,1]);
for (let x of set)
{
    console.log(x);
}