Develop Reference

loop through array to create image slider with vanilla javascript

I am trying to create an image carousel and I want the images to loop through the array. The code is clearly working because the "no click" alert shows but I don't understand what I am doing wrong.
Here is JS. I know the problem is most likely the if statement. I'm a beginner in JS and haven't quite understood how to code that bit properly. In some sort of pseudo code, it would ideally be "if btn is clicked, then show the next image".
let images = ["img1.jpg", "img2.jpg", "img3.jpg"];
let img = images.length;
let x = 0;
function whenClicked(e) {
for (let i = 0; i < img; i++) {
if (x == 0) {
document.getElementById("img1").style.backgroundImage = ++img;
} else alert("no click!")
}
}
const btnLeft = document.getElementById("btn-left");
const btnRight = document.getElementById("btn-right");
btnLeft.addEventListener("click", whenClicked);
btnRight.addEventListener("click", whenClicked);
And here HTML.
<div class="slide-container">
<div class="slide" id="img1">
<i class="fas fa-arrow-circle-left fa-3x" id="btn-left" ></i>
<i class="fas fa-arrow-circle-right fa-3x" id="btn-right" ></i>
</div>
</div>
CSS.
.slide-container {
}
.slide {
height: 789px;
width: 100%;
background-size: cover;
background-position: center;
background-repeat: no-repeat;
}
.slide:nth-child(1) {
background-image: url(../img/img1.jpg);
}
.slide:nth-child(2) {
background-image: url(../img/img2.jpg);
}
.slide:nth-child(3) {
background-image: url(../img/img3.jpg);
}
#btn-left {
position: absolute;
top: 400px;
}
#btn-right {
position: absolute;
left: 1380px;
top: 400px;
}
Suggestions on what to do to improve would be deeply appreciated!

You might be overcomplicating your approach. Try to keep track of which image is currently being shown and what image should be next. You are almost doing this, with I assume is your intent, with the x variable. This is a great way to select an image from the array by simply doing images[x], which translates to images[0] at the start.
So if you want to develop a system which changes the background image of the slide, then your buttons would have to change the value of the x variable. Let's give that variable a more clear name, like currentIndex which represents the current index in the images array. Or to be clear, the current image we are seeing.
When your right button is clicked, you'll want the next image. The next images in the images array is images[1]. All you have to do is update the currentImage value with +1 or ++ and select the next image with images[currentIndex] to get the next one.
Same goes for the left button which should remove 1 from the currentImage with either -1 or -- to go back one index in the images array. Then select the image the same way with images[currentIndex].
Now for both these buttons you'll need to check if you go past the start or the end of the images array. currentIndex cannot be lower than 0 and with 3 images in the array, the currentIndex value should not be higher than 2, since we are counting with [0, 1, 2] in the images array.
Below I've made an implementation of this system. I hope this is what you intended to make. If I haven't been clear or you have question, then don't hesitate to ask.
let images = ["img1.jpg", "img2.jpg", "img3.jpg"];
let amountOfImages = images.length;
let currentIndex = 0;
const slide = document.getElementById("img1");
const btnLeft = document.getElementById("btn-left");
const btnRight = document.getElementById("btn-right");
function prevImage() {
if (currentIndex > 0) { // Can't go lower than 0.
currentIndex--;
updateImage();
}
}
function nextImage() {
if (currentIndex < amountOfImages - 1) { // Can't go higher than the amount of images present.
currentIndex++;
updateImage();
}
}
function updateImage() {
slide.style.backgroundImage = images[currentIndex];
}
btnLeft.addEventListener("click", prevImage);
btnRight.addEventListener("click", nextImage);

let currentImage = 0;
let images = ["img1.jpg", "img2.jpg", "img3.jpg"];
function whenClicked(e) {
if(e.target.id == 'btn-left') {
currentImage--;
} else {
currentImage++;
}
if(currentImage > images.length-1) {
currentImage = 0;
}
if(currentImage < 0) {
currentImage = images.length-1;
}
document.getElementById("img1").style.backgroundImage = url('img/'+images[currentImage]);
}

Meeting Calendar | How to take care of the overlapping meetings to show in the calendar?

Sorry for the long question.
I have tried to create a meetings on a calendar for a day. I need help to take care of the overlapping intervals.
The code I have written in following :
HTML
<body>
<div id="timeline"></div>
<div id="calendar" class="calendar">
</div>
</body>
CSS
.calendar {
border: 1px solid black;
position: absolute;
width: 600px;
height: 1440px;
left: 60px;
}
.event {
position: absolute;
float: left;
width: 100%;
overflow: auto;
border: 0px solid red;
}
#timeline {
position: absolute;
float: left;
}
JS
function getRandomColor() {
var letters = '0123456789ABCDEF'.split('');
var color = '#';
for (var i = 0; i < 6; i++) {
color += letters[Math.floor(Math.random() * 16)];
}
return color;
}
function creatTimeline(tl) {
var i = 0;
while (i < tl.length) {
var divEl = document.createElement('div');
divEl.style.width = '50px';
divEl.style.height = '120px';
divEl.style.border = '0px solid yellow';
divEl.innerHTML = tl[i];
var timeLine = document.getElementById('timeline');
timeLine.appendChild(divEl);
i++;
}
}
function appendEventDivs(eventArr) {
var i = 0;
while (i < eventArr.length) {
var eventEl = document.createElement('div');
eventEl.className = 'event';
eventEl.style.height = eventArr[i].height;
eventEl.style.top = eventArr[i].top;
eventEl.style.background = eventArr[i].color;
eventEl.style.width = eventArr[i].width;
eventEl.style.left = eventArr[i].left;
eventEl.innerHTML = 'Meeting' + eventArr[i].id;
var cl = document.getElementById('calendar');
cl.appendChild(eventEl);
i++;
}
}
function collidesWith(a, b) {
return a.end > b.start && a.start < b.end;
}
function checkCollision(eventArr) {
for (var i = 0; i < eventArr.length; i++) {
eventArr[i].cols = [];
for (var j = 0; j < eventArr.length; j++) {
if (collidesWith(eventArr[i], eventArr[j])) {
eventArr[i].cols.push(i);
}
}
}
return eventArr;
}
function updateEvents(eventArr) {
eventArr = checkCollision(eventArr);
var arr = [];
arr = eventArr.map(function(el) {
//just to differentiate each event with different colours
el.color = getRandomColor();
el.height = (el.end - el.start) * 2 + 'px';
el.top = (el.start) * 2 + 'px';
el.width = (600 / el.cols.length) + 'px';
return el;
});
return arr;
}
var events = [{
id: 123,
start: 60,
end: 150
}, {
id: 124,
start: 540,
end: 570
}, {
id: 125,
start: 555,
end: 600
}, {
id: 126,
start: 585,
end: 660
}];
var timeline = ['9AM', '10AM', '11AM', '12Noon', '1PM', '2PM', '3PM', '4PM', '5PM', '6PM', '7PM', '8PM', '9PM'];
function getEvents (eventArr) {
eventArr.sort(function(a, b) {
return a.start - b.start;
});
eventArr = updateEvents(eventArr);
appendEventDivs(eventArr);
console.log(eventArr);
//PART 1 - function returning the eventArr with all the required attributes
return eventArr;
};
creatTimeline(timeline);
getEvents(events);
Working fiddle here
Can anybody guide me how to take care of the overlapping intervals so that they appear side-by-side and not on top of each other.
Thanks in advance.

You need to figure out in which column each of the events should be before you can determine their width or left-position. To do this, you need to also store which of the colliding events came before each event:
function checkCollision(eventArr) {
for (var i = 0; i < eventArr.length; i++) {
eventArr[i].cols = [];
eventArr[i].colsBefore=[];
for (var j = 0; j < eventArr.length; j++) {
if (collidesWith(eventArr[i], eventArr[j])) {
eventArr[i].cols.push(j);
if(i>j) eventArr[i].colsBefore.push(j); //also list which of the conflicts came before
}
}
}
return eventArr;
}
Now, we can figure out the column of each event. Once we've done that, we can figure out how wide they should be, and with that, the horizontal positioning should be easy. This should be done inside your updateEvents function. I've got more detailed explanation commented in the comments of the code below.
function updateEvents(eventArr) {
eventArr = checkCollision(eventArr);
var arr=eventArr.slice(0); //clone the array
for(var i=0; i<arr.length; i++){
var el=arr[i];
el.color = getRandomColor();
el.height = (el.end - el.start) * 2 + 'px';
el.top = (el.start) * 2 + 'px';
if(i>0 && el.colsBefore.length>0){ //check column if not the first event and the event has collisions with prior events
if(arr[i-1].column>0){ //if previous event wasn't in the first column, there may be space to the left of it
for(var j=0;j<arr[i-1].column;j++){ //look through all the columns to the left of the previous event
if(el.colsBefore.indexOf(i-(j+2))===-1){ //the current event doesn't collide with the event being checked...
el.column=arr[i-(j+2)].column; //...and can be put in the same column as it
}
}
if(typeof el.column==='undefined') el.column=arr[i-1].column+1; //if there wasn't any free space, but it ito the right of the previous event
}else{
var column=0;
for(var j=0;j<el.colsBefore.length;j++){ //go through each column to see where's space...
if(arr[el.colsBefore[el.colsBefore.length-1-j]].column==column) column++;
}
el.column=column;
}
}else el.column=0;
}
//We need the column for every event before we can determine the appropriate width and left-position, so this is in a different for-loop:
for(var i=0; i<arr.length; i++){
arr[i].totalColumns=0;
if(arr[i].cols.length>1){ //if event collides
var conflictGroup=[]; //store here each column in the current event group
var conflictingColumns=[]; //and here the column of each of the events in the group
addConflictsToGroup(arr[i]);
function addConflictsToGroup(a){
for(k=0;k<a.cols.length;k++){
if(conflictGroup.indexOf(a.cols[k])===-1){ //don't add same event twice to avoid infinite loop
conflictGroup.push(a.cols[k]);
conflictingColumns.push(arr[a.cols[k]].column);
addConflictsToGroup(arr[a.cols[k]]); //check also the events this event conflicts with
}
}
}
arr[i].totalColumns=Math.max.apply(null, conflictingColumns); //set the greatest value as number of columns
}
arr[i].width=(600/(arr[i].totalColumns+1))+'px';
arr[i].left=(600/(arr[i].totalColumns+1)*arr[i].column)+'px';
}
return arr;
}
Working Fiddle: https://jsfiddle.net/ilpo/ftbjan06/5/
I added a few other events to test different scenarios.
Oh, and by the way, absolutely positioned elements can't float.

You already know the top and height of every event, so you could map the calendar and check an event already exist within the area it will occupy, then offset the left value by the number of existing events.

Delay on jquery keyup?

I'm trying to create my own "autocomplete", but when I type a letter (eg. w for word), then there's a splitsecond delay - enough to annoy the eye.
Here's my testcode:
CSS:
#txtSearchAutocomplete {
background-color: white !important;
position: absolute;
top: 0;
width: 100%;
font-size: 20px !important;
border: none !important;
color: gray;
}
#txtSearch {
background-color: transparent !important;
position: absolute;
top: 0;
width: 100%;
font-size: 20px !important;
border: none !important;
}
HTML:
<span style="position: relative; display: inline-block; width:100%; top: -18px;">
<input type="text" id="txtSearchAutocomplete" disabled >
<input type="text" id="txtSearch">
</span>
JS:
$(document).ready(function($) {
$("#txtSearch").focus();
$("#txtSearch").keyup(function(e) {
var autocomplete = ['word', 'excel'];
var $txtAutocomplete = $("#txtSearchAutocomplete");
var txt = $("#txtSearch").val().trim().toLowerCase();
$txtAutocomplete.val("");
if (txt == "") return;
for (i = 0; i < autocomplete.length; i++) {
var entry = autocomplete[i];
if (entry.indexOf(txt) == 0) {
$txtAutocomplete.val(entry);
break;
};
};
});
});
And a fiddle sample:
https://jsfiddle.net/25gwz1qu/1/
If you type in the letter w - delete it - type it again and so on, then you will notice a small delay. It might seam that the delay is a bit longer in IE.
Any idea how to get rid of this delay?
Thanks

The reason for the delay you are seeing is because the event triggers once the user lets go of the key. In that case, the oninput is the way to go. The event triggers when the textbox input changes.
$("#txtSearch").on('input', function(e) { ... })

Please take a look on my solution with comments that explain why I did those changes and here is a Working Fiddle.
On my machine the auto-complete is almost instant after those modifications.
$(document).ready(function($) {
// i had moved all selectors outside the function so the havy dom selection will happen only once
var autocomplete = ['word', 'excel'];
var $txtAutocomplete = $("#txtSearchAutocomplete");
var $searchElement = $("#txtSearch");
$searchElement.focus();
// In Jquery on works faster than on key up, cause user lets go of the key.
$searchElement.on('input',function(e) {
var txt = $searchElement.val().trim().toLowerCase();
// I had replaced the element to be a div and not a input cause the div element is much light weight and faster to draw for the browser
$txtAutocomplete.text("");
if (txt == "")
return;
for (i = 0; i < autocomplete.length; i++) {
var entry = autocomplete[i];
if (entry.indexOf(txt) == 0) {
$txtAutocomplete.text(entry);
break;
};
};
});
});

try this,
$(document).ready(function($) {
$("#txtSearch").focus();
$("#txtSearch").on('input',function(e) {
var autocomplete = ['word', 'excel'];
var $txtAutocomplete = $("#txtSearchAutocomplete");
var txt = $("#txtSearch").val().trim().toLowerCase();
$txtAutocomplete.val("");
if (txt == "") return;
for (i = 0; i < autocomplete.length; i++) {
var entry = autocomplete[i];
if (entry.indexOf(txt) == 0) {
$txtAutocomplete.val(entry);
break;
};
};
});
});

Scroll to position WITHIN a div (not window) using pure JS

PURE JS ONLY PLEASE - NO JQUERY
I have a div with overflow scroll, the window (html/body) never overflows itself.
I have a list of anchor links and want to scroll to a position when they're clicked.
Basically just looking for anchor scrolling from within a div, not window.
window.scrollTo etc. don't work as the window never actually overflows.
Simple test case http://codepen.io/mildrenben/pen/RPyzqm
JADE
nav
a(data-goto="#1") 1
a(data-goto="#2") 2
a(data-goto="#3") 3
a(data-goto="#4") 4
a(data-goto="#5") 5
a(data-goto="#6") 6
main
p(data-id="1") 1
p(data-id="2") 2
p(data-id="3") 3
p(data-id="4") 4
p(data-id="5") 5
p(data-id="6") 6
SCSS
html, body {
width: 100%;
height: 100%;
max-height: 100%;
}
main {
height: 100%;
max-height: 100%;
overflow: scroll;
width: 500px;
}
nav {
background: red;
color: white;
position: fixed;
width: 50%;
left: 50%;
}
a {
color: white;
cursor: pointer;
display: block;
padding: 10px 20px;
&:hover {
background: lighten(red, 20%);
}
}
p {
width: 400px;
height: 400px;
border: solid 2px green;
padding: 30px;
}
JS
var links = document.querySelectorAll('a'),
paras = document.querySelectorAll('p'),
main = document.querySelector('main');
for (var i = 0; i < links.length; i++) {
links[i].addEventListener('click', function(){
var linkID = this.getAttribute('data-goto').slice(1);
for (var j = 0; j < links.length; j++) {
if(linkID === paras[j].getAttribute('data-id')) {
window.scrollTo(0, paras[j].offsetTop);
}
}
})
}
PURE JS ONLY PLEASE - NO JQUERY

What you want is to set the scrollTop property on the <main> element.
var nav = document.querySelector('nav'),
main = document.querySelector('main');
nav.addEventListener('click', function(event){
var linkID,
scrollTarget;
if (event.target.tagName.toUpperCase() === "A") {
linkID = event.target.dataset.goto.slice(1);
scrollTarget = main.querySelector('[data-id="' + linkID + '"]');
main.scrollTop = scrollTarget.offsetTop;
}
});
You'll notice a couple of other things I did different:
I used event delegation so I only had to attach one event to the nav element which will more efficiently handle clicks on any of the links.
Likewise, instead of looping through all the p elements, I selected the one I wanted using an attribute selector
This is not only more efficient and scalable, it also produces shorter, easier to maintain code.
This code will just jump to the element, for an animated scroll, you would need to write a function that incrementally updates scrollTop after small delays using setTimeout.
var nav = document.querySelector('nav'),
main = document.querySelector('main'),
scrollElementTo = (function () {
var timerId;
return function (scrollWithin, scrollTo, pixelsPerSecond) {
scrollWithin.scrollTop = scrollWithin.scrollTop || 0;
var pixelsPerTick = pixelsPerSecond / 100,
destY = scrollTo.offsetTop,
direction = scrollWithin.scrollTop < destY ? 1 : -1,
doTick = function () {
var distLeft = Math.abs(scrollWithin.scrollTop - destY),
moveBy = Math.min(pixelsPerTick, distLeft);
scrollWithin.scrollTop += moveBy * direction;
if (distLeft > 0) {
timerId = setTimeout(doTick, 10);
}
};
clearTimeout(timerId);
doTick();
};
}());
nav.addEventListener('click', function(event) {
var linkID,
scrollTarget;
if (event.target.tagName.toUpperCase() === "A") {
linkID = event.target.dataset.goto.slice(1);
scrollTarget = main.querySelector('[data-id="' + linkID + '"]');
scrollElementTo(main, scrollTarget, 500);
}
});
Another problem you might have with the event delegation is that if the a elements contain child elements and a child element is clicked on, it will be the target of the event instead of the a tag itself. You can work around that with something like the getParentAnchor function I wrote here.

I hope I understand the problem correctly now: You have markup that you can't change (as it's generated by some means you have no control over) and want to use JS to add functionality to the generated menu items.
My suggestion would be to add id and href attributes to the targets and menu items respectively, like so:
var links = document.querySelectorAll('a'),
paras = document.querySelectorAll('p');
for (var i = 0; i < links.length; i++) {
links[i].href=links[i].getAttribute('data-goto');
}
for (var i = 0; i < paras.length; i++) {
paras[i].id=paras[i].getAttribute('data-id');
}

Get only the ellipsis text using jquery

Nice code, just wondered if it is possible to query and get the ellipsis text (i.e. with the dots in and not the original text)?
If I add the text
This is a long sentence
and (using the relevant css for ellipsis) it gets shortened to
This is a long sen ...
Is there a way to get the text
"This is a long sen ..."
from the $("p") DOM object rather than the original text?

Try that:
function getEllipsis(command, characters) {
for (var i = command.length; i >= 0; i--) {
if (command.substring(0, i).length < characters) {
if (i < command.length) {
command = command.substring(0, i) + "...";
}
return command;
}
}
}
console.log(getEllipsis("I am a long sentence",16))
console.log(getEllipsis("But I am even longer",20))

I have a rough draft that needs some browser-specific tweaking.
JavaScript:
jQuery.fn.getShowingText = function () {
// Add temporary element for measuring character widths
$('body').append('<div id="Test" style="padding:0;border:0;height:auto;width:auto;position:absolute;display:none;"></div>');
var longString = $(this).text();
var eleWidth = $(this).innerWidth();
var totalWidth = 0;
var totalString = '';
var finished = false;
var ellipWidth = $('#Test').html('…').innerWidth();
var offset = 7; // seems to differ based on browser (6 for Chrome and 7 for Firefox?)
for (var i = 0;
(i < longString.length) && ((totalWidth) < (eleWidth-offset)); i++) {
$('#Test').text(longString.charAt(i));
totalWidth += $('#Test').innerWidth();
totalString += longString.charAt(i);
if(i+1 === longString.length)
{
finished = true;
}
}
$('body').remove('#Test'); // Clean up temporary element
if(finished === false)
{
return totalString.substring(0,totalString.length-3)+"…";
}
else
{
return longString;
}
}
console.log($('#ellDiv').getShowingText());
CSS:
#Test {
padding:0;
border:0;
height: auto;
width: auto;
position:absolute;
white-space: pre;
}
div {
width: 100px;
white-space: nowrap;
border: 1px solid #000;
overflow:hidden;
text-overflow:ellipsis;
padding:0;
}
With the caveat that the offset needs to change depending on the browser, unless someone can figure out what is causing it.
I suspect letter-spacing or similar?