Category Archives: JavaScript

JavaScript30—Day 3

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 3 — CSS Variables + JS: Demo - Day 3

- - declares variables in CSS as $ in php or var in javaScript. You declare:
```
:root{
--basecolor:#ffc600;
}
```
and call it out like this:
```
p {
 backround-color: var(--basecolor);
}
```
:root is the deepest level you can go.
If you want update your e.g. style attribute according to input via javaScript variable and name should have the same name, otherwise it wont work:
- -basecolor:#ffc600;
NodeList vs array document.querySelectorAll gives NodeList. The difference between NodeList and array is that array gives you all kinds and longer list of methods like map,reduce. List of methods for array: List of methods for NodeList:

Day 3 code on github.

JavaScript30—Day 2

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 2 — CSS-JS clock: Demo - Day 2

Date() gives a chance to get hours, minutes, seconds etc.

const now = new Date();
seconds = now.getSeconds();
minutes = now.getMinutes();
hours = now.getHours()

transform-origin vs transform:rotate() The first one sets the point around which the transformation takes place. Rotate() is driven by center of the element. More about MDN transform-origin.

Day 2 code on github.

JavaScript30—Day 7

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 7 — Array Cardio 2: Demo - Day 7

Array.prototype.some(); is there at least one match? Returns true or false.
Array.prototype.every(); every single item in array matches to the condition or not? Returns true or false.
console.log({variable}); - in console can be seen like
```
isAdult:true
```
Array.prototype.find(); Find is like filter, but instead returns just the one you are looking for

With all these methods we can use array method without if-statment— because method returns true or false. So, instead this:

const comment = comments.find(function(comment){
      if (comment.id === 823423){
         return true;
      }

    });

we can write:

const comment = comments.find(comment => comment.id ===823423);

Deleting from array: First use Array.prototype.findIndex() and then use splice()

 const commentB = comments.findIndex(comment=>comment.id ===823423);
 //returns 1
comments.splice(0, 1);

or creating new array, spread and slice(),

const index = comments.findIndex(comment=>comment.id ===542328);
    const newComments = [
      ...comments.slice(0,index),
      ...comments.slice(index + 1)
    ];
    console.table(newComments);

Day 7 code on github.

JavaScript30—Day 15

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 15 — LocalStorage and EventDelegation: Demo - Day 15

Form and submit: if it is form you should listen to submit—event and not click.

this.querySelector('[name=item]') So if we have form like this:

We can grab input value like this:

var input = document.querySelector('.js-it');
var inputValue = input.value;

or using this and parthensis:

var input = (this.querySelector['name=it']).value;

plates=[]: We have function
```
function populateList(plates=[], plateList){
 //code here
    
  }
```
plates=[] is an empty object and if we forget to pass something in, it won't broke our JavaScript
.map(): creates from one array another array.
.join(''): returns .map() array as a string.
will still be checked— any existence of attribute checked will check it.
localStorage accepts only strings. If it's something else in Console->Application-> Local Storage you'll see [object Object]. It can be stringified:
```
localStorage.setItem('items', JSON.stringify(items));
```
JSON. parse() is opposite to JSON.stringify(), itparses string to origin value or object.

setting value as condition:

const items = JSON.parse(localStorage.getItem('items')) || [];

Day 15 code on github.

JavaScript30—Day 28

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Sorting band names without a/an/the Lessons from Day 28 — Video Speed Scrubber: Demo - Day 28

This tutorial won't work with YouTube videos because you can't put embeded video into video-tag.
video-tag won't play .avi-format
e.pageY : MouseEvent interface returns the Y (vertical) coordinatein pixels of the event relative to the whole document
element.offsetTop: is the number of pixels from the top of the closest relatively positioned parent element.
element.offsetHeight: is a measurement in pixels of the element's CSS height, including border, padding and the element's horizontal scrollbar (if present, if rendered).
HTMLMediaElement.playbackRate: property sets the rate at which the media is being played back. A value of 1.0 indicates normal speed and if negative—it's played back backwards. If it's too fast or slow— audio is muted.

Day 28 code on github.

JavaScript30 – Day 17

Regex to replace a/an/the with ' '

function strip(bandName){

  return bandName.replace(/^(a |the |an )/i,'').trim();

}

Ternary operator - ?: is called ternary operator
```
return strip(a) > strip(b) ? 1 : -1
```

How to write a function in three ways:

//first
const sortedBands = bands.sort(function(a,b){
 return strip(a) > strip(b) ? 1 : -1
});

//as arrow-function
const sortedBands = bands.sort ((a,b) =>{
 return strip(a) > strip(b) ? 1 : -1
});

// if the only thing you are doing in function is returning - you can do implicit return
const sortedBands = bands.sort((a,b) => strip(a) > strip(b) ? 1 : -1);

Output with/without commas

sortedBands.map(band => `${band}`);
//will give you commas after the names:
["Anywhere But Here
", "The Bled
", "Counterparts
", "The Devil Wears Prada
", "The Midway State
", "Norma Jean
", "Oh, Sleeper
", "An Old Dog
", "Pierce the Veil
", "The Plot in You
", "Say Anything
", "A Skylit Drive
", "We Came as Romans"]

sortedBands.map(band => `${band}`).join('');
//will give
Anywhere But Here
The Bled
Counterparts
The Devil Wears Prada
The Midway State
Norma Jean
Oh, Sleeper
An Old Dog
Pierce the Veil
The Plot in You
Say Anything
A Skylit Drive
We Came as Romans

Day 17 code on github.

JavaScript30 – Day 9

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 9: Demo - Day 9 Some console tricks (on Win Ctrl+Shift+I)

Interpolated strings in console.log()

    console.log('Hello');
    console.log('I am a %s string', 'awesome' );
    var string = "awesome";
    console.log(`I am ${string} string`);

Styling console.log()

    console.log('%c I am awesome string', 'color:#BADA55; font-size:20px;');

Warning—console.warn()
```
    console.warn("No!");
```
Error—console.error()
```
    console.error("Smth went wrong!");
```

Info—console.info()

 console.info("console.info() is for providing info!");

Clearing console—console.clear()— simpliest way to clear console.

Testing—console.assert() - returns only if the statemeny is false

    console.assert (1===1, 'That is true'); // won't show anything
    console.assert (1===2, 'That is wrong'); //shows text

    const p = document.querySelector('p');
    console.assert (p.classList.contains('whatever'), 'No such class!');

Viewing DOM elements—console.dir

 console.log(p); //shows actual element itself
 console.dir(p); // shows all the element's attributes and methods

Image shows only a fragment of console.dir():

Grouping together—console.group()—uncollapsed version

dogs.forEach(dog => {
      console.group(`${dog.name}`); // uncollapsed
      console.log(`This dog is ${dog.age} years old`);
      console.groupEnd(`${dog.name}`); // important to put otherwise inside each other

    });

Grouping together—console.group()—collapsed version

dogs.forEach(dog => {
      console.groupCollapsed(`${dog.name}`); // collapsed
       console.log(`This dog is ${dog.age} years old`);
      console.groupEnd(`${dog.name}`); // important to put otherwise inside eacother

    });

Hugo is clicked open to show provided information:

Counting—console.count()

    console.count('S');
    console.count('S');
    console.count('R');
    console.count('S');
    console.count('S');
    console.count('T');
    console.count('T');
    console.count('S');
    console.count('L');

Timing—console.time()— how long operation takes time

console.time('fetching data');
    fetch('https://api.github.com/users/wesbos')
    .then(data => data.json())
    .then(data =>{
      console.timeEnd('fetcing data');
      console.log(data);
    });

console.table()—displays tabular data as table

console.log(dogs);
console.table(dogs);//same size of objects

Day 9 code on github.

JavaScript30 – Day 10

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 10: Demo - Day 10

let var - another type of variable in JavaScript. Variables declared by let have as their scope the block in which they are defined, as well as in any contained sub-blocks . In this way, let works very much like var. The main difference is that the scope of a var variable is the entire enclosing function—MDN link
inBetween = !inBetween is same as inbetween = true. It's also called a flag variable - a flag variable, in its simplest form, is a variable you define to have one value until some condition is true, in which case you change the variable's value.
Warning‐change vs click I started it by myself and in this point - it didn't react anyhow.
```
if(e.shiftKey && this.checked){
	console.log("jep");
}
```
As I listened to the 'change', I changed it to 'click' and voila - it worked.

Day 10 code on github.

JavaScript30 – Day 8

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 8: Demo - Day 8

Organizing your variables and values as an array:

[lastX, lastY] = [e.offsetX, e.offsetY];

is the same as:

lastX = e.offsetX;
lastY = e.offsetY;

hsl— h is for hue (between 0-360), s is for saturation and l is for lightness.
strokeStyle and lineWidth It's ctx.strokeStyle for color, but ctx.lineWidth for width.

direction != direction and direction = !direction - let's assume that direction is true:

direction != direction // true isn't equal to true
direction = !direction  // change direction's value to opposite - if true, now be false

Debugging:
- console.log(canvas)- as it didn't do anything and no spelling mistakes so far - turned out I had accidentally deleted the -tag.
- inside draw() - console.log(e) after the condition, if I console it before it gives me true and false, but I only want one of them.
- calling out draw function - addEventListener('mousemove') worked but nothing else didn't care if it was false or true. Possible ways to debug:
```
inside function draw(){
	console.log(isDrawing);
	if(isDrawing ="false") return;
}
```
  It turned out to be spelling mistake in addEventListener('mousedown'),()=> isDARwing = true); and not addEventListener('mousedown'),()=> isDRAwing = true);

Day 8 code on github.

JavaScript30 – Day 1

JavaScript30 is 30-day vanilla javaScript coding challenge by Wes Bos (@wesbos). Actually I saw this challenge at the beginning of the year and thought "no, won't take it because probably I won't finish it" ... but here I am. I'm still not sure about finishing, but if I can get it through till the end of the year - well done! The purpose of these posts is to reflect my troubles and moments of ahhaa. Lessons from Day 1: Demo - Day 1

const– so far I've used only var to define variables. Const values cannot be changed or redeclared.
` back-ticks and template literals:
```
const audio = document.querySelector(`audio[data-key="${e.keyCode}"]`);
```
This is the part I struggled the most. If I copied it, it worked, if wrote it on my own– it didn't. And I couldn't understand why? And no ideas what to google for. Fortunately there is always Twitter. Yes, I know there are different types of quotes - ",',´. But turns out there are also backticks - on Win you can type them ALT + (num keyboard on right) 9+ (num keyboard on right) 6 or you have to Google for which key to press. `${variable}` as templating literals allowing embedded variables.
http://keycode.info/ to find quickly keyboard's key code.
if(!Obj) return; – stop the function if the Obj is null (there is no such object). I think I'm familiar with the concept but why I haven't it used before?

arrow-function So this function:

 allAs.forEach(function(element) {
             element.classList.add('playing');
        });

can be written as an arrow-function:

 allAs.forEach(element => element.classList.add('playing'));

<kbd> is html—tag for keyboard input
Adding audio files I had to add .mp3 to the end.
```
	
```
As I changed the word to "javascript" I had two "A"s. It got me some time to figure out that I can't detect if it is the first A or the second one by keypress. So, I had to modify my code: a) check if it is A b) if it is get all the A-s (document.querySelectorAll) c) and each of them add class "playing"
```
 if(e.keyCode =="65"){
         // get all letter A                 
         allAs = document.querySelectorAll(`div[data-key="${e.keyCode}"]`);
         allAs.forEach(element => element.classList.add('playing'));
         
    } else {
       key.classList.add('playing');
    }
```

Day 1 code on github.