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Module #1 - The Basics

LOADING AND RUNNING JAVASCRIPT

add <script> tag just before the </body> tag.

<body>
  ...
  <script src="./some.js"></script>
</body>

VARIABLES

  • var (value can be updated)
  • let (value can be updated)
  • const (value can't be updated)
var name = "Wes";
let age = 100;
const cool = true;

TYPE OF VARIABLES:

  • String:

    represent letter, paragraphs, phases, etc. Can be declared with quotes, double-quotes or back ticks.

    const name = "Wes";
const middle = "topher";
const last = `Bos`;

    sentence
    with "\ esc", quotes, single quotes and backtick option:
    sentence = She´s so "cool"

    const sentence = 'she´s so "cool"';
const sentence = 'she´s so "cool"';
const sentence = `She's so "cool"`;

    concatenation & interpolation

    const hello = `hello my name is ${variable_name} nice yo meet you. I'm ${
  30 + 5
} years old`;

  • Numbers:

    Numbers on Javascript includes float, integers, etc ...
    there are all the basic operation (addition, subtraction, multiplication and division).

    let a = 10 + 10; // addition
let b = 20 - 10; // subtraction
let c = 10 * 10; // multiplication
let d = 100 / 10; // division
let e = 1000 % 3; // modulo

    Javascript have helper methods like:

    Math.round(20.5); //result 21, round number up or down
Math.floor(20.2); //result 20, will give you the lower
Math.ceil(20.9); // result 21, will give you the upper
Math.random(); // gives random number between 0 and 1

    NaN is an other number, that means Not a number

    let a = 10 / "dog";
console.log(a);

// result: NaN

  • Objects

    Everything in javascript is an object, are use for collections of data or functionality.

    const person {
  firstName = 'Cesar',
  lastName = 'Gomez',
  age = '35'
};

    order doesn't matter in objects, we can access to the properties, the easiest way is:

    person.firstName; // access to the first name properties
person.lastName; // access to the last name properties
person.age; // access to the age properties

  • Null and Undefined

    Undefined: comes when you try to access toa variable that has been created, but not set.

    let dog;
console.log(dog); //result should be undefined

    Null: is a value of nothing

    let somethingNull = null;

  • Booleans and equality

    Booleans: is a value of true or false, can be manually set or calculate:

    //manually set
let isDrawing = true;

//calculate
const age = 18;
const ofAge = age > 19;
console.log(ofAge); // result should be false

    Equality: we have:

    • = (setting or updating a variable)
    • == (it compares the value but not the type of )
    • === (compares the value and type of )
    // =
let dog = "Sharon";

// ==
"10" == 10; //result is true, it compares the value but not the type of (both values are 10)

// ===
"10" === 10; // result is false, compares value and type of (first one is string, second one is number)

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