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Welcome to JavaScript

JavaScript is used everywhere. You can use JavaScript to select any element,5 attribute, or text from an HTML page. It allows you to make web pages more interactive by accessing and modifying the content and markup used in a web page while it is being viewed in the browser.

Objects

In JavaScript Variables are containers for data values. Objects are variables too except objects can contain many values. Let's look at an example below:


            var person = {
              firstName:"John",
              lastName:"Doe",
              age:50,
              eyeColor:"blue"
            };
        

Arrays

We just learned a little about objects. Arrays are "list-like objects"; they are basically single objects that contain multiple values stored in a list. If we didn't have arrays, we'd have to store every item in a separate variable. Let's look at an example below:


var sequence = [1, 1, 2, 3, 5, 8, 13];
  for (var i = 0; i < sequence.length; i++) {
  console.log(sequence[i]);
}

For Loops

Loops are used to run the same bit of code over and over again, each time with a different variable. For loops loop through a block of code a number of times. Let's look at a For Loop that adds all numbers 1-50.


        let sum = 0;

        for (let i = 1; i <= 50; i++) {
            sum = sum + i
        }
        console.log(sum)
                

If Else Conditionals

the If Else executes a statement if a specified condition is truthy. If the condition is falsy , another statement can be executed. Let's look at an If Else statement that looks at the temperature and determines if we should wear a jacket.


let temperature = 75;

if (temperature < 70) {
    console.log('Wear a jacket!');
} else {
    console.log('No jacket necessary!');
}
                

Functions

A function is code that can be called by other code or by itself. When a function is called, arguments are passed to the function as input, and the function can optionally return an output. This is also an object. Let's look at a basic function.


let array = ['This', 'is', 'really', 'cool'];

function cool() {
    console.log('This')
    console.log('is')
    console.log('really')
    console.log('cool')
}

cool()
                

Switches

A Switch is another type of conditional. It is very similar to If Else statements. It uses cases and breaks instead of Ifs and Elses.


switch (dessert) {
  case "pie":
      console.log('Pie, pie, me oh my!')
      break;
  case "cake":
      console.log('Cake is great!')
      break;
  case "ice cream":
      console.log('I scream for ice cream!')
      break;
      default:
      console.log('Not on the menu')
}