Can someone please tell me why when I click on the [s] href created next to the list of names (myhand) generated it always says selection and i are 5?
var printDD = function(myhand, mydiv){
var dtext = "";
for(var i = 0; i < myhand.length; i++){
dtext += '[s]' + myhand[i] + ', ';
}
mydiv.html(dtext);
for(var i = 0; i < myhand.length; i++){
$('#dd'+i).click(function(){
selection = i;
console.log("sel: " + selection + " i: " + i);
});
}
}
You want to take a look at JavaScript closure inside loops – simple practical example. As the answer to that question says, you can create a function to return one, or you can use inline function invocation in the for loop like so:
for(var i = 0; i < myhand.length; i++) {
$('#dd'+i).click((function(x) {
return function () {
selection = x;
console.log("sel: " + selection + " x: " + x);
}
}(i)));
}
Because the value of i is determined at the time the click handler is run. So it will always have the value of myhand.length - 1, which is the state you left i in after the for-loop.
Related
Is there a way to include variables in each iteration of a javascript loop? For example if I put this code into a loop
if (e1) {item_text += '{id:"' + id[1] + '",lvl:' + e1lvl + '},<wbr>'}
if (e2) {item_text += '{id:"' + id[2] + '",lvl:' + e2lvl + '},<wbr>'} // etc
and do something like
for (n = 0; n < id.length; n++) {
if (e/*concat var e w/var n?*/) {
item_text += '{id:"' + id[1] + '",lvl:' + e/*concat var e w/var n?*/lvl + '},<wbr>'
}
}
Is there a way to change the number in the var names (e1 -> e2 etc) each iteration or do i just have to keep it the long way and write everything out on its own line?
It would be possible, though highly not recommended, to use eval to come up with the variable name:
const e1lvl1 = 'foo';
const e2lvl1 = 'bar';
for (let i = 1; i < 3; i++) {
console.log(eval('e' + i + 'lvl1'));
}
But it would be better to fix your script's architecture so that this isn't necessary: put each e#lvl into an array, and then access the appropriate index of the array on each iteration:
const elvl = [
'foo',
'bar'
];
let item_text = '';
for (let i = 0; i < elvl.length; i++) {
item_text += 'lvl: ' + elvl[i] + '\n';
}
console.log(item_text);
Arrays/Objects exist in javascript for a reason! Simplify your code. There is no reason to have e1, e1l, e2... as variables. Add them to an object and access them by key, or add them to an array, and loop through them. There are many javascript functions as well that will allow you to ensure all elements match a certain condition.
function submit() {
var e = {};
var idx = 28;
for (var i = 0; i <= 24; i++) {
e[i] = {};
e[i].key = document.getElementById(`ench${i}`).checked
e[i].value = $.trim(form.elements[idx].value)
idx += 2;
}
// Check condition
if (Object.values(e).some(e => e.key)) {
//One of the checked items was true
}
}
I would agree that you should change your code to use arrays.
To answer your question though, since your e1 and e1lvl variables look to be global scope, you can access them like this
window["e1"]
window["e1lvl"]
Give this a try
for (n = 0; n < id.length; n++) {
if (window["e" + n]) {
item_text += '{id:"' + id[n] + '",lvl:' + window["e" + n + "lvl"] + '},<wbr>';
}
}
I have this array of objects here that I am traversing and want to display a match if the person at the current index has an age within +/- 10 years of anyone else in the array. However, when I run it, it says "Cannot read property 'age' of undefined." Where did I go wrong?
function findmatches() {
var n = USERS.length;
for (var i = 0; i < n; i++) {
var currName = USERS[i].firstName;
var currAge = USERS[i].age;
var currGender = USERS[i].gender;
for (var c = 0; c < 10; c++) {
if (((USERS[c].age) + 10) <= currAge) {
document.getElementById("showmatches").innerHTML += currName + " matched to >> " + USERS[i].firstName + " " + USERS[i].lastName + " \n";
break;
}
}
}
}
What exactly is your second for loop supposed to do?
In the code you posted, it iterates through first 10 users in the USERS array. I assume it has less users than that, so at some point USERS[c] is undefined, and you're trying to access USERS[c].age.
Is there a way to loop this four times to make it shorter? I am trying to change the class from standing to sitting and then back again one at a time.
if(sitting > 0) {
$('.standing:first-of-type').removeClass('standing').addClass('sitting');
} else {
$('.sitting:first-of-type').removeClass('sitting').addClass('standing');
}
if(sitting > 1) {
$('.standing:nth-of-type(2)').removeClass('standing').addClass('sitting');
} else {
$('.sitting:nth-of-type(2)').removeClass('sitting').addClass('standing');
}
if(sitting > 2) {
$('.standing:nth-of-type(3)').removeClass('standing').addClass('sitting');
} else {
$('.sitting:nth-of-type(3)').removeClass('sitting').addClass('standing');
}
if(sitting > 3) {
$('.standing:nth-of-type(4)').removeClass('standing').addClass('sitting');
} else {
$('.sitting:nth-of-type(4)').removeClass('sitting').addClass('standing');
}
You can use :lt and :gt selectors.
:lt(index) select all elements at an index less than index within the matched set. :gt(index) select all elements at an index greater than index within the matched set.From jQuery Docs
As the class sitting should be added to all the elements having class .standing whose index is less than the sitting variable value, :lt selector can be used with the variable sitting to select such elements. Then addClass() and removeClass() can be used on the jQuery set of elements to add and remove the passed classes respectively.
$('.standing:lt(' + sitting + ')').removeClass('standing').addClass('sitting');
$('.sitting:gt(' + sitting + ')').removeClass('sitting').addClass('standing');
Well, you can do with an ugly for-loop:
function toggleSitting(sitting){
var initial = 0;
var final = 3;
for(var i = initial; i <= final; i++){
$('.standing:nth-of-type(' + (i+1) +')')
.toggleClass('standing', sitting < i)
.toggleClass('sitting', sitting > i);
}
}
toggleSitting(sitting);
This is just a draft and it's untested, but there is a logic in what you are trying to do. Once you find the logic, you just have use it in a loop. Like that :
var condition;
for(var i = 0; i < 4; i++){
condition = sitting > i;
$('.standing:nth-of-type(' + (i + 1) + ')').toggleClass('standing', !condition).toggleClass('sitting', condtion);
}
Maybe Something like this:
var numberOfPlaces = 4;
for(var i=0; i<sitting && i<numberOfPlaces ; i++){
$('.standing:nth-of-type(' + (i+1) + ')').removeClass('standing').addClass('sitting');
}
for(var i=sitting; i<numberOfPlaces ; i++){
$('.sitting:nth-of-type(' + (i+1) + ')').removeClass('sitting').addClass('standing');
}
or this:
var numberOfPlaces = 4;
for(var i=0; i<numberOfPlaces; i++){
if(i<sitting){
$('.standing:nth-of-type(' + (i+1) + ')').removeClass('standing').addClass('sitting');
}else if(i>=sitting){
$('.sitting:nth-of-type(' + (i+1) + ')').removeClass('sitting').addClass('standing');
}
}
Do you have HTML and CSS to accompany that ?
You can use a variable to specify the 'nth' of type:
$('.standing:nth-of-type(' + i + ')')
although not sure that that works for the case where i = 1. You might need first-of-type there.
Without the CSS and HTML it isn't clear exactly what you want to do.
You might want to look at this also:
https://css-tricks.com/almanac/selectors/n/nth-of-type/
I have a problem to use the operator += in an object.
Because i have to change the variable dynamically i use an object as variable.
But if i use the += operator the first element in the output always gets undefined. I think thats because the object is initialized empty.
What is the best solution to prevent to output that element ?
Here goes my example code:
var dynamicVariable = {};
var group = "apples";
for(var i = 1; i<5; i++)
{
dynamicVariable[group] += " Apple" + i + "<br>";
}
document.getElementById("fruits").innerHTML = dynamicVariable[group];
jsFiddle
This is happening because dynamicVariable[group] has the value undefined before you start appending to it. undefined + " Apple1" is "undefined Apple1".
You need to initialize it to an empty string first:
dynamicVariable[group] = "";
for(var i = 1; i<5; i++) {
dynamicVariable[group] += " Apple" + i + "<br>";
}
Here is my code. I do not quite understand why the for loop runs only once, both inner and outer. nodeList.length and innerNodeList.length show appropriate values when I generate alert messages. I see that both i and j do not increment beyond 0. Kindly point out anything wrong with the code.
function getCategoryElements() {
var newCategoryDiv = document.getElementById("category");
var nodeList = newCategoryDiv.childNodes;
for (var i = 0; i < nodeList.length; ++i) {
var innerNodeList = nodeList[i].childNodes;
alert("innerNodeList Length" + innerNodeList.length.toString());
for (var j = 0; j < innerNodeList.length; ++j) {
if (innerNodeList[j].nodeName == "SELECT") {
alert("inside select Node value " + innerNodeList[j].nodeValue.toString());
document.getElementById("newCategories").value =
document.getElementById("newCategories").value + '<%=delimiter%>' + innerNodeList[j].nodeValue;
} else if (innerNodeList[j].nodeName == "TEXTAREA") {
document.getElementById("newCategoriesData").value =
document.getElementById("newCategoriesData").value + '<%=delimiter%>' + innerNodeList[j].nodeValue;
}
}
}
}
var newCategoryDiv, nodeList, innerNodeList, innerNode, i, j;
newCategoryDiv = document.getElementById("category");
nodeList = newCategoryDiv.childNodes;
for (i = 0; i < nodeList.length; ++i) {
innerNodeList = nodeList[i].childNodes;
alert("innerNodeList Length" + innerNodeList.length.toString());
for (j = 0; j < innerNodeList.length; ++j) {
innerNode = innerNodeList[j];
if (innerNode.nodeName === "SELECT") {
alert("inside select Node value " + innerNode.nodeValue.toString());
document.getElementById("newCategories").value += '<%=delimiter%>' + innerNode.nodeValue;
} else if (innerNode.nodeName === "TEXTAREA") {
document.getElementById("newCategoriesData").value += '<%=delimiter%>' + innerNode.nodeValue;
}
// Will this work?
alert('Does this alert appear');
}
}
I took the liberty to refactor your code and clean it up a little bit. In case you're not aware, all variables have function scope in Javascript, so no matter where you declare them within a single function, Javascript treats them as if the variable declaration is the first statement.
It appears that your code is syntactically correct, and so I think that the most logical place to look for a problem is that there could be an error occurring after the last alert function call.
In order to check this, try adding another alert function call to the end of the inner loop. If it doesn't run, you'll know this is the case.