Skip to content

Latest commit

 

History

History
216 lines (161 loc) · 5.23 KB

week_06.md

File metadata and controls

216 lines (161 loc) · 5.23 KB

Week 6

Day 1

Primitives and Data Types

Javascript

  • Javascript is named the way it is because it was a marketing ploy using the Java name
  • Javascript was a scripting language that was created to compete with applets
  • Ecmascript is the official name for Javascript
  • Works with REST API for data layer, serverless technology, etc
  • Javascript can help you build and do everything

Hoisting

  • Hoisting is when you can call a function or a variable before it is declared example: var hoist; console.log(hoist); hoist = 'The variable has been hoisted.";

Variables

  • var is for global variables that will change
  • let is for global variables that will chance
  • const is for global variables that will NOT change. const is good for security purposes and sometimes required. Const is for global variables that will NOT change
  • example for let:
function whatIsLet(sum) {
	let whatIsThis = ' This can be changed is within lexical - or local - scope.';
	return sum + 1;
	console.log(whatIsThis);
}

Data types

  • string represents textual data 'hello', "hello world!" etc
  • number is an integer or a floating-point number 3, 3.234, 3e-2 etc.
  • bigInt is an integer with arbitrary precision 900719925124740999n , 1n etc.
  • boolean is any of two values: true or false
  • undefined is a data type whose variable is not initialized. An example is: let a;
  • null denotes a null value let a = null
  • symbol data type whose instances are unique and immutable let value = Symbol('hello');
  • object consists of key-value pairs of collection of data let student - {};
  • NAN is a property of a global object (kind of like the planet Pluto because some consider it a data type and some do not);

Resources

Day 2

Conditionals

  • if this, then do this
  • format is:
if (name === "John) {
   console.log("red")
} else if (name === "Aaron") {
   console.log("blue")
} else {
    console.log("green")
}

Switch statement is used instead of using a long line of conditionals

The format of it is below:

// switch
const fruit = 'Pears';
switch (fruit) {
	case 'Oranges':
		console.log('Oranges are $0.59 a pound.');
		break;
	case 'Mangoes':
	case 'Papayas':
		console.log('Mangoes and papayas are $2.79 a pound.');
		// expected output: "Mangoes and papayas are $2.79 a pound."
		break;
	default:
		console.log(`Sorry, we are out of ${fruit}.`);
}

Equals Signs

  • one equal sign is assigning something to a variable
  • two equals signs is comparing something but not data types
  • explicit equals is === It also compares data types

Day 3

Arrays

  • Example:
var newArray = [1, 2, 3, 4];
/*an array is enclosed by brackets and each value is separated by commas. Arrays are declared
with a variable by using let, const, or var depending on whether the items in the array with be
changed or not.*/
  • Arrays start at [0] index
  • Example:
var numbers = [1, 2, 3, 5, 8]; //array of numbers
var cars = ['Mazda', 'Honda', 'Chevy', 'Ford']; //array of strings
var honda = cars[3];
/*assigning a new variable with the value from the cars array. honda will be equal to the string
"Ford" because the array starts at [0] index*/
  • There are a number of array methods built into Javascript. Here are a few of them:
arr.push(...items) – adds items to the end,
arr.pop() – extracts an item from the end,
arr.shift() – extracts an item from the beginning,
arr.unshift(...items) – adds items to the beginning.

arr.splice(start[, deleteCount, elem1, ..., elemN])
/*It modifies arr starting from the index start: removes deleteCount elements and then inserts elem1,
 ..., elemN at their place. Returns the array of removed elements.*/

//Example of splice
let arr = ["I", "study", "JavaScript"];
arr.splice(1, 1); // from index 1 remove 1 element

console.log( arr ); // ["I", "JavaScript"]

Day 4

Loops

Definition

  • Loops are like interstate loops. It takes you around and around until you reach your desired exit point It is a piece of logic that dictates how many times to run something until you reach the designated end point

For Loop

  • for loop is the easiest form of a loop. Very close to an "if" statement but it has more options.
  • Example:
for(condition; end condition; change){
    // do it, do it now
}
  • Another example:
for (var integer = 0; integer < 10; integer = integer++) {
	console.log('yay!');
}

While Loop

  • Used when you need to break logic. It doesn't increment.
  • Example:
var i = 0,
	x = '';
while (i < 5) {
	x = x + 'The number is ' + i;
	i++;
}

Do While

  • Example
var i = 0;
do {
	console.log(i + ' ');
	i++; // incrementing i by 1
} while (i < 100);

For of Loop

  • Example
const array1 = ['a', 'b', 'c'];
for (const element of array1) {
	console.log(element);
}

Break and Continue

  • break; //stops the loop
  • continue; //skips this iteration and goes to the next iteration

Resources