I am running a function that populates several paragraph tags on a webpage with the days of the week. The function takes an array of days which is populated based on the current day (i.e. if today is Thursday, get the next 7 days in order).
My problem is that for some reason, I am unable to populate these tags. I have checked to make sure that the array is getting populated and the list is being iterated through. While both of these are true, none of the Inner HTML of the tags are being changed.
HTML:
<p class="mb-1" id="forecastDay1" runat="server">Day</p>
<p class="mb-1" id="forecastDay2" runat="server">Day</p>
JavaScript Function:
function populatePage(arry) {
var i;
for (i = 0; i < arry.length - 1; i++) {
var id = "forecastDay" + i.toString();
document.getElementById(id).innerHTML = arry[i].toString();
}
}
I have also tried it this way:
document.getElementById("forecastDay" + i.toString()).innerHTML = arry[i].toString();
You do not need toString in JavaScript.
Also, arrays start at 0, while your elements start at 1. You have to compensate that difference.
function populatePage(arry) {
var i;
for (i = 0; i < arry.length; i++) {
var id = "forecastDay" + (i + 1);
document.getElementById(id).innerHTML = arry[i];
}
}
// Test it
populatePage(["Day 1", "Day 2"]);
<p class="mb-1" id="forecastDay1" runat="server">Day</p>
<p class="mb-1" id="forecastDay2" runat="server">Day</p>
There are a few things wrong with your code:
The first value of i is 0. Since there is not element #forecastDay0, getElementById will return null. Trying to access innerHTML of null will throw an error, thus breaking the for loop and every thing after it. You should check your console when something doesn't work, it's a great way to debug.
The check for the for loop should be i < arry.length not i < arry.length - 1.
You don't need any of the toString calls.
That being said, here is how it should be:
function populatePage(arry) {
var i;
for (i = 0; i < arry.length; i++) {
var id = "forecastDay" + (i + 1); // i + 1 instead of just i. The casting to strings is done automatically
document.getElementById(id).textContent = arry[i]; // use textContent as there isn't really any HTML
}
}
Related
I was trying to display members' names in the div element after 3 seconds by using for loop with setTimeout() function. But I'm getting an undefined values of the names array. And even the value of var i displaying 4. I don't know why. Can anyone explain to me why and how to fix that.?
Thanks in advance!
JS Code:
function members() {
var arr = ["Joseph","John","Kumar","Shiva"];
var i;
for(i = 0; i < arr.length; i++) {
setTimeout(function() {
console.log("Member = " + i + ". " + arr[i]);
document.getElementById("Names").innerHTML = "Member = " + i + ". " + arr[i];
}, 3000);
}
}
members();
<div id="Names"></div>
First, Because var is a function scope ( not block scope like for loop ), when the setTimeout execute after 3 sec, the loop will be ended and the value of i will be equal to the arr.length, and arr[arr.lenght] will equal to undefined.
To solve this issue, one solution is using let instead of var.
Second, If you want to add the members to HTML, you need to use += to concatenate with the previous string not = which will re-initialize the innerHTML
const names = document.getElementById("Names");
function members() {
var arr = ["Joseph","John","Kumar","Shiva"];
for(let i = 0; i < arr.length; i++) {
setTimeout(function() {
console.log("Member = " + i + ". " + arr[i]);
document.getElementById("Names").innerHTML += `Member = ${(i + 1)}. ${arr[i]}<br />`;
}, 3000);
}
}
members();
<div id="Names"></div>
I think better solution for you here is to execute a function after 3 seconds, rather then putting the timeout inside for loop.
That was what was causing your issue, as the var is a function scoped variable. So by putting timeout inside of for loop, the last element would be undefined since your script would read the last element as arr.length, which is 4, and you don't have arr[4], hence it is undefined.
Also, your innerHTML was not written properly, if you want to print multiple values, you need to use innerHTML += instead of innerHTML = because innerHTML = will always print the last value from your loop, because it erases the innerHTML of your element in each new iteration.
I modified your code snippet below.
https://codepen.io/Juka99/pen/VwxpXwL
EDIT - I changed the code to correctly declare variables below but nothing seems to have changed
I've written code using a for-loop that has to satisfy a number of criteria before executing what's within it. The problem is that, somewhere along the way, the code is getting stuck inside one of the loops, causing the computer to crash.
I've tried breaking the loop but this doesn't seem to help.
function compareKeypoints(varifiedKeypoints) {
outer_loop: for (i = 0; i < varifiedKeypoints.length; i++) {
let initialKeypoint = varifiedKeypoints[i];
for (j = 0; j < varifiedKeypoints.length; j++) {
let comparisonKeypoint = varifiedKeypoints[j];
if (initialKeypoint.part != comparisonKeypoint.part) {
if (Math.abs(comparisonKeypoint.position.x - initialKeypoint.position.x) <= 20
&& Math.abs(comparisonKeypoint.position.y - initialKeypoint.position.y) <= 20) {
if (keypointsCompatible(initialKeypoint.part, comparisonKeypoint.part)) {
console.log("Activating part: " + initialKeypoint.part);
console.log("Activated part: " + comparisonKeypoint.part);
let keypointPair = {
point_1: initialKeypoint.part,
point_2: comparisonKeypoint.part
}
console.log("Pushing parts!");
activeParts.push(keypointPair);
console.log("breaking loop!");
break outer_loop;
console.log("Loop NOT broken!!");
}
}
}
}
}
if (activeParts.length > 0) {
console.log(activeParts);
}
}
function keypointsCompatible(keypoint_1, keypoint_2) {
var outcome = true;
if (activeParts.length > 0) {
compatibility_loop: for (i = 0; i < activeParts.length; i++) {
if (Object.values(activeParts[i]).includes(keypoint_1) && Object.values(activeParts[i]).includes(keypoint_2)) {
console.log(keypoint_1 + " and " + keypoint_2 + " are not compatible because they already exist as " + activeParts[i].point_1 + " and " + activeParts[i].point_2 + " respectively");
outcome = false;
break compatibility_loop;
console.log("Compatibility NOT broken!!");
}
}
}
console.log("Compatibility outcome is " + outcome);
return outcome;
}
The code is suppose to take two values in the same array and compare them. If a number of conditions are met, including if they're a certain distance apart from one another, they will be pushed into a secondary array. If the values already appear in the secondary array, which the keypointCompatible function is suppose to determine, the loop should either continue looking for other candidates or stop before being called again. For some reason, however, the code is getting stuck within the keypointCompatible function when it detects that the values have already appeared in the secondary array and the console will repeatedly print "Compatibility is false" until the browser crashes.
Working Solution
Use let or const instead of var or nothing. Your issue may be related to closures and variables reused between loops. Make sure you use let or const in your loops too. for (let i=0).
When you use let or const, the runtime will create a new instance every time the block or loop iterates. However, using var will reuse the internal allocation.
So what happens with the standard var is the multiple closures or loops each use the same instance of the variable.
Unless you want the var behavior, always use let or const.
Another Solution
Put a newline after the label compatibility_loop
Still Another Solution
The first function is pushing into activeParts. The second function is looping activeParts. This can go on forever, or longer than expected. Pushing into the array could possibly make the loop limit never reached.
Put a log on the length of activeParts in the second function to see if it is growing out of control.
Your code should be OK if varifiedKeypoints.length has reasonable value. And all internal variables are declared properly!
You have two loops (this inner can start at j=i+1 to save time and multiple calculations) with few conditions inside.
function compareKeypoints(varifiedKeypoints) {
outer_loop: for (let i = 0; i < varifiedKeypoints.length; i++) {
let initialKeypoint = varifiedKeypoints[i];
for (let j = i+1; j < varifiedKeypoints.length; j++) {
let comparisonKeypoint = varifiedKeypoints[j];
I have some file contents I'd like to pass on to my server using a javascript function. In the file, there are many empty lines, or those which contain useless text. So far I read every line in as a string stored in an array.
How do I then loop through that content skipping multiple lines such as lines 24,25, 36, 42, 125 etc. Can I put these element id's into an array and tell my for loop to run on every element except these?
Thanks
you can't tell your for loop to iterate all, but skip certain elements. it will basically just count in any direction (simplified) until a certain critera has been met.
you can however put an if inside your loop to check for certain conditions, and chose to do nothing, if the condition is met. e.g.:
(pseudo code below, beware of typing errors)
for(var line=0; line < fileContents.length; line++) {
if(isUselessLine(line)) {
continue;
}
// process that line
}
the continue keyword basically tells the for loop to "jump over" the rest of the current iteration and continue with the next value.
The isUselessLine function is something you'll have to implement yourself, in a way, that it returns true, if the line with the given linenumber is useless for you.
You can try this its not much elegent but will suerly do the trick
<html>
<body>
<p>A loop which will skip the step where i = 3,4,6,9.</p>
<p id="demo"></p>
<script>
var text = "";
var num = [3,4,6,9];
var i;
for (i = 0; i < 10; i++) {
var a = num.indexOf(i);
if (a>=0) {
continue;
}
text += "The number is " + i + "<br>";
}
document.getElementById("demo").innerHTML = text;
</script>
</body>
You could use something like this
var i = 0, len = array1.length;
for (; i < len; i++) {
if (i == 24 || i == 25) {
array1.splice(i, 1);
}
}
Or you can have an another array variable which got all the items that need to be removed from array1
Another method:
var lines = fileContents.match(/[^\r\n]+/g).filter(function(str,index,arr){
return !(str=="") && uselessLines.indexOf(index+1)<0;
});
If you have many indices to skip, and this depends on the elements of the array, you could write a function that returns the number of elements to skip over for each index in that array (or returns 1, if no skipping required):
for ( let i = 0;
i < array.length;
i += calcNumberOfIndicesToSkip( array, i )){
// do stuff to the elements that aren't
// automatically skipped
}
function calcNumberOfIndicesToSkip( array, i ){
// logic to determine number of elements to skip
// (this may be irregular)
return numberOfElementsToSkip ;
}
In your case:
// skip the next index (i+1)?
for ( let i=0; i<array.length; i+=skipThisIndex(i+1) ){
// do stuff
}
function skipThisIndex(i){
const indicesToSkip = [ 24, 25, 36, 42, 125 ];
return 1 + indicesToSkip.includes(i);
}
// returns 1 if i is not within indicesToSkip
// (there will be no skipping)
// => (equivalent to i++; normal iteration)
// or returns 1 + true (ie: 2) if i is in indicesToSkip
// => (index will be skipped)
My code should insert HTML content in all divs that have a predefined class name, without using jQuery and at least compatible with IE8 (so no getElementsbyClass).
The html:
<div class="target">1</div>
<div class="target">2</div>
<div class="target">3</div>
<div class="target">4</div>
The javascript:
var elems = document.getElementsByTagName('*'), i;
for (wwi in elems) {
if((' ' + elems[wwi].className + ' ').indexOf(' ' + "target" + ' ') > -1) {
elems[wwi].innerHTML = "YES";
//elems[wwi].innerHTML = "<div>YES!</div>";
}
}
You can try it here.
As you can see inside each div the word YES is printed. Well the if you comment elems[wwi].innerHTML = "YES"; and replace that for elems[wwi].innerHTML = "<div>YES!</div>" the code fails. I suppose is because inserting div elements modify the DOM and in consequence the FOR cycle fails. Am i right?
Well i can solve this pretty ugly by recalling the for cycle each time i make an innerHTML, and when i insert the code i can add a class (like data-codeAlreadyInserted=1) to ignore the next time the FOR pass in that div. But again, this is pretty much a very bad solution since for an average site with many tags I can even freeze the user browser.
What do you think? lets suppose i dont know the amount of tags i insert on each innerHTML call.
"I suppose is because inserting div elements modify the DOM and in consequence the FOR cycle fails. Am i right?"
Pretty much. Your elems list is a live list that is updated when the DOM changes. Because you're adding a new div on every iteration, the list keeps growing and so you never get to the end.
To avoid this, you can either do a reverse iteration,
for (var i = elems.length-1; i > -1; i--) {
// your code
}
or convert the list to an Array.
var arr = [];
for (var i = 0, len = list.length; i < len; i++) {
arr.push(elems[i]);
}
for (i = 0; i < len; i++) {
// your code
}
Another way is to use replaceChild instead of innerHTML. It works better and it's way faster:
var newEl = elem[wwi].cloneNode(false);
newEl.innerHTML = html;
elem[wwi].parentNode.replaceChild(newEl, elem[wwi]);
You can take a copy of the live node list:
var nodes = [];
for (var i = 0, n = elems.length; i < n; ++i) {
nodes.push(elems[i]);
}
and then use a proper for loop, not for ... in to iterate over the array:
for (var i = 0, n = nodes.length; i < n; ++i) {
...
}
for ... in should only be used on objects, not arrays.
what I'm hoping to achieve is to increase a count and then append that to the DOM on every pass through using each(). What I have at the moment is the final count added at the end. For example.
Say I have 100 divs, for every pass through it should add the new count as it counts it, like so 1,2,3,4,5,6,7... and so on. But at the moment it counts all the objects and just appends 100 at the end. Please can someone point me in the direction to where I'm going wrong?
I've added a very basic version of what I'm hoping to achieve below... also here is a JSbin (I tried jsfiddle but it seems to be down for me) .
$(".toCount").each(function(i){
$("#count").text(i + 1);
});
$('input').on('click',function () {
var len = $(".toCount").length;
var arr = [];
for (var i = 0; i < len; i++ ) {
arr.push(i+1);
}
$('#count').text(arr.join());
});
I don't know what you mean by 1, 2, 3 ... in case that you want to count the elements step by step you can use setInterval function:
$('input').on('click',function () {
var l = $(".toCount").length,
$c = $('#count'),
i = 0;
var t = setInterval(function() {
i++;
$c.text(i);
if (i === l) clearInterval(t);
}, 10);
});
http://jsbin.com/eronel/17/edit
use append();
Insert content, specified by the parameter, to the end of each element in the set of matched elements.
in your case text() is replacing your div's text so u get 100 at the end ..
$("#count").append(i + 1);
Use append
$("#count").append(i + 1);