Develop Reference

Javascript- Dynamic variable loop

I'm trying to reduce the amount of code I repeat.
Currently I have the below:
var item1H = $(".item-1").height();
var item1W = $(".item-1").height();
$(".item-1 .text").css('margin-left', -item1W/2);
$(".item-1 .text").css('margin-bottom', -item1H/2);
var item2H = $(".item-2").height();
var item2W = $(".item-2").height();
$(".item-2 .text").css('margin-left', -item2W/2);
$(".item-2 .text").css('margin-bottom', -item2H/2);
I'm looking to put this into a for loop where the variable number would count up to whatever number I needed it to stop.

You can make function like this and use whenever you want
toSetMargin(".item-2")
toSetMargin(".item-2")
function toSetMargin(objStr){
var widthTmp = $(objStr + ' .text').height();
var heightTmp = $(objStr + ' .text').height();
obj.css('margin-left', -widthTmp/2);
obj.css('margin-bottom', -heightTmp/2)
}
This code not impact any other code.

You could use $('[class^="item-"]') to get all the elements that have a class that starts with item-, and the loop over them
$('[class^="item-"]').each(function(){
var $elem = $(this);
var item1H = $elem.height();
var item1W = $elem.width();
$elem.find('.text').css({'margin-left': -item1W/2,'margin-bottom':-item1H/2});
});

Ooh boy, one of these problems. This should help (untested):
for(i=1;i<=STOPPING_NUMBER;i++){
window["item"+i+"H"] = $(".item-"+i).height();
window["item"+i+"W"] = $(".item-"+i).width(); //Was height, accident?
$(".item-"+i+" .text").css('margin-left', 0-window["item"+i+"W"]/2); //Hope this works lol
$(".item-"+i+" .text").css('margin-bottom', 0-window["item"+i+"H"]/2);
}

Guessing these lines:
var item1W = $(".item-1").height();
var item2W = $(".item-2").height();
Should have been:
var item1W = $(".item-1").width();
var item2W = $(".item-2").width();
You could do something like:
function setCSS(item,attr,val) {
$(item +" .text").css(attr, (val * -1)/2);
}
var i, max = 10;
for(i=1;i<=max;i++) {
setCSS(".item-"+ i,"margin-left",$(".item-"+ i).width());
setCSS(".item-"+ i,"margin-bottom",$(".item-"+ i).height());
}
Or something less flexible within the function:
function setCSS(item,w,h) {
$(item +" .text").css("margin-left", (w * -1)/2);
$(item +" .text").css("margin-bottom", (h * -1)/2);
}
var i, max = 10;
for(i=1;i<=max;i++) {
setCSS(".item-"+ i,$(".item-"+ i).width()),$(".item-"+ i).height());
}

Something like this should be pretty acceptible in your case, I guess:
for (var i = 1, len = someN; i < len; i++) {
var $item = $('.item-' + i);
$item.find('.text').css({
'margin-left': -$item.width() / 2,
'margin-bottom': -$item.height() / 2
});
}

JS: Create Objects in loop with iterator

I want to create some objects like object_point1, object_point2, ...
with a for loop that split a string with x and y coords.
How can i use iterates to create the name of objects?
Thanks
var vMsg = req.body.myMessage;
var fields = vMsg.split(/\n/);
var myobjct = new Object();
myobject.PointCount=parseFloat(paramsCoords);
for (var ii=0; ii<fields.length; ii++)
{
var coord=fields[ii].split(/\t/);
//console.info ("X" + coord[0]);
//console.info ("Y" + coord[1]);
var object_Point[ii] = new Object();
object_Point[ii].x_m=parseFloat(coord[0]);
object_Point[ii].y_m=parseFloat(coord[1]);
myobject.Polygon_Point[ii]=object_Point[ii];
}
At the moment i use this construction:
for (var ii=0; ii
var coord=fields[ii].split(/\t/);
var objPolygon_Point = new Object()
objPolygon_Point["point" + ii] = new Object();
objPolygon_Point["point" + ii].x_m=parseFloat(coord[0]);
objPolygon_Point["point" + ii].y_m=parseFloat(coord[1]);
if (ii=='1')
{
myobject.Polygon_Point1=objPolygon_Point["point" + ii];
}
if (ii=='2')
{
myobject.Polygon_Point2=objPolygon_Point["point" + ii];
}
// ii==3, ii==4, .......
}

You can generate dynamic object names in the global scope like:
Browser:
var ii = 11
, x = 123
, y = 234;
window['Object_Point' + ii] = {
x : parseFloat(x),
y : parseFloat(y)
}
console.log(Object_Point11);
console.log(window.Object_Point11);
// Object {x: 123, y: 234}
node.js
> var i = 12;
> global['MyObj'+i] = { hello : 'world' };
> console.log(MyObj12);
> console.log(global.MyObj12);
// { hello: 'world' }
see node.js global variables?
But rather than using window or global, you might want to use your own object
> var i = 12, myObj = {};
> myObj['MyObj'+i] = { hello : 'world' };
> console.log(myObj.MyObj12);
// { hello: 'world' }

I directly used your example. I'll suggest to create middle-map object. I.e. something like holder of all the points. Using the global namespace is not a good practice.
var vMsg = req.body.myMessage;
var fields = vMsg.split(/\n/);
var myobjct = new Object();
myobject.PointCount=parseFloat(paramsCoords);
var points = {};
for (var ii=0; ii<fields.length; ii++)
{
var coord=fields[ii].split(/\t/);
//console.info ("X" + coord[0]);
//console.info ("Y" + coord[1]);
var point = points["point" + ii] = new Object();
point.x_m = parseFloat(coord[0]);
point.y_m = parseFloat(coord[1]);
myobject.Polygon_Point[ii] = point;
}

How do I empty global arrays used in a pop up slideshow?

I've created a program where you can choose a set of images by checking checkboxes. The image URL's and the alt-texts are stored in two arrays. When clicking av button on the HTML-page you open a new window that calls on the arrays with window.opener.
When closing the new window I would like to empty the arrays. Otherwise the pictures chosen in the first round are displayed in the slideshow when opening it the second time. I understand you can empty arrays by this method: array.length= 0;
But where do I add the code? I'm quite lost. I'm pasting the code, perhaps someone can give me a hand.
var imgUrlList = [], imgTextList = [], //These arrays need to be emptied
windVar = null;
function init() {
var tags, i, openWindow;
tags = document.getElementsByClassName("unmarkedImg");
openWindow = document.getElementById("slideShowBtn");
openWindow.onclick = savePicsForSlideshow;
for (i = 0; i < tags.length; i++) {
tags[i].parentNode.onmouseover = showLargePict;
tags[i].parentNode.onmouseout = hideLargePict;
}
}
window.onload = init;
function showLargePict() {
var largePictTagDiv = this.getElementsByClassName("innerBox")[0];
var largePictTagParentDiv = largePictTagDiv.parentNode;
var imgTag = largePictTagParentDiv.getElementsByTagName('img')[0];
var checkBoxlargePict = largePictTagDiv.getElementsByTagName('input')[0];
if (checkBoxlargePict.checked)
imgTag.className = "markedImg";
else imgTag.className = "unmarkedImg";
largePictTagDiv.style.visibility = "visible";
} // End showLargePict
function hideLargePict() {
var largePictTag;
largePictTag = this.getElementsByClassName("innerBox")[0];
largePictTag.style.visibility = "hidden";
}
function savePicsForSlideshow() {
var innerBoxes = document.getElementsByClassName("innerBox");
for (i = 0; i < innerBoxes.length; i++) {
checkBoxlargePict = innerBoxes[i].getElementsByTagName('input')[0];
if (checkBoxlargePict.checked) {
var imgTagSrc = innerBoxes[i].getElementsByTagName('img')[0].src;
imgUrlList.push(imgTagSrc);
var spanTagText = innerBoxes[i].getElementsByTagName('span')[0].innerHTML;
imgTextList.push(spanTagText);
}
}
if (imgTextList.length > 0) {
newWindow(500, 600, "slideshow.htm");
}
}
function newWindow(width, height, filename) {
var windowProperties;
windowProperties = "top=100,left=100,toolbar=no,location=no,status=no,menubar=no,scrollbars=no,resizable=no,width=" + width + ",height=" + height;
if (windVar != null) if (windVar.closed == false) windVar.close();
windVar = window.open(filename, "", windowProperties);
}
Please excuse my programming and English grammar shortcomings. I'm new to javascript.
//Henrik, Göteborg, Sweden.

At the beginning of the savePicsForSlideshow function, empty out each array.
imgUrlList.length = 0;
imgTextList.length = 0;

You can check if thw window is close with the property closed of the object window
if(window.closed)
{
array.length = 0;
}

assign parameter value of an object javascript

I have been looking at this code for a long time trying to figure this out, but I am having no luck. This issue is that I want to assign a value to the parameter boxId. When I click on a box in the webpage an alert will come up displaying that id. I have tried many things, but nothing seems to work. I'm a beginner, so I feel at this point there just must be something that I don't know how to do.
constructor function:
function Box (boxId, name, color, number, coordinates) {
this.boxId = boxId;
this.name = name;
this.color = color;
this.number = number;
this.coordinates = coordinates;
}
global variables:
var boxes = [];
var counter = 0;
var boxId = 0;
init function:
window.onload = init;
function init() {
var generateButton = document.getElementById("generateButton");
generateButton.onclick = getBoxValues;
var clearButton = document.getElementById("clearButton");
clearButton.onclick = clear;
}
function to get values and create new boxes:
function getBoxValues() {
var nameInput = document.getElementById("name");
var name = nameInput.value;
var numbersArray = dataForm.elements.amount;
for (var i = 0; i < numbersArray.length; i++) {
if (numbersArray[i].checked) {
number = numbersArray[i].value;
}
}
var colorSelect = document.getElementById("color");
var colorOption = colorSelect.options[colorSelect.selectedIndex];
var color = colorOption.value;
if (name == null || name == "") {
alert("Please enter a name for your box");
return;
}
else {
var newbox = new Box(boxId, name, color, number, "coordinates");
boxes.push(newbox);
counter++;
var boxId = counter;
}
addBox(newbox);
var data = document.getElementById("dataForm");
data.reset();
}
function that adds boxes to the page:
function addBox(newbox) {
for (var i = 0; i < newbox.number; i++) {
var scene = document.getElementById("scene");
var div = document.createElement("div");
div.className += " " + "box";
div.innerHTML += newbox.name;
div.style.backgroundColor = newbox.color;
var x = Math.floor(Math.random() * (scene.offsetWidth-101));
var y = Math.floor(Math.random() * (scene.offsetHeight-101));
div.style.left = x + "px";
div.style.top = y + "px";
scene.appendChild(div);
div.onclick = display;
}
}
function to display alert when box is clicked:
function display(e) {
var a = e.target;
alert(a.counter);
}
function to clear boxes:
function clear() {
var elems = document.getElementsByClassName("box");
for ( k = elems.length - 1; k >= 0; k--) {
var parent = elems[k].parentNode;
parent.removeChild(elems[k]);
}
}
All of the other functions work just fine. I keep running into the id showing up as "undefined" when I click it, or the counter displaying "0" in the console log, for everything I've tried.

You can do it like this.
First, in addBox() embed boxId as an tag's attribute like this:
div.setAttribute('data-boxId', newbox.boxId);
Then in display() you can retrieve it back:
alert(e.target.getAttribute('data-boxId'));
Please tell if you do not prefer this approach and I will post an alternative (closure things).
Edit: Add jsfiddle example http://jsfiddle.net/runtarm/8FJpU/

One more try. Perhaps if you change:
var boxId = counter;
to
boxId = counter;
It will then use the boxId from the outer scope instead of the one defined in the function getBoxValues()

how to use an event object to dispaly information about a DOM element

I want to be able to click on a box (the boxes are created through code, and receive values from a form) in the webpage and display information about the box. I am working on a display() function that uses an event object and an alert to display information about the box. So far, I've had multiple odd failures in my attempt to do this, which leads me to believe that I'm not accessing object attributes correctly. I'm a beginner, so this could be really obvious, but thanks for the help.
constructor function:
function Box (counter, name, color, number, coordinates) {
this.counter = counter;
this.name = name;
this.color = color;
this.number = number;
this.coordinates = coordinates;
}
Global variables:
var boxes = [];
var counter = 0;
Init function:
function init() {
var generateButton = document.getElementById("generateButton");
generateButton.onclick = getBoxValues;
var clearButton = document.getElementById("clearButton");
clearButton.onclick = clear;
}
Function that gets values from the form:
function getBoxValues() {
var nameInput = document.getElementById("name");
var name = nameInput.value;
var numbersArray = dataForm.elements.amount;
for (var i = 0; i < numbersArray.length; i++) {
if (numbersArray[i].checked) {
number = numbersArray[i].value;
}
}
var colorSelect = document.getElementById("color");
var colorOption = colorSelect.options[colorSelect.selectedIndex];
var color = colorOption.value;
if (name == null || name == "") {
alert("Please enter a name for your box");
return;
} else {
var newbox = new Box(counter, name, color, number, "coordinates");
boxes.push(newbox);
counter++;
/*for(m = 0; m < boxes.length; m++) {
counter.newbox = boxes[m];
}*/
}
addBox(newbox);
var data = document.getElementById("dataForm");
data.reset();
}
function that assigns attributes to the boxes:
function addBox(newbox) {
for (var i = 0; i < newbox.number; i++) {
var scene = document.getElementById("scene");
var div = document.createElement("div");
div.className += " " + "box";
div.innerHTML += newbox.name;
div.style.backgroundColor = newbox.color;
var x = Math.floor(Math.random() * (scene.offsetWidth-101));
var y = Math.floor(Math.random() * (scene.offsetHeight-101));
div.style.left = x + "px";
div.style.top = y + "px";
scene.appendChild(div);
div.onclick = display;
//console.log(newbox);
//shows all of the property values of newbox in the console
//console.log(div); shows that it is an object in the console
//console.log(div.hasAttribute(number)); says false
}
}
display function:
function display(e) {
// alert(e.target); says its an html object
//alert(e.target.className); works - says "box"
//alert(e.target.hasAttribute(name)); says false
}
I've included some of the things i've found in comments.

The event object only gives you the name not a reference to the element. So... a couple of things.
First if you want to be browser agnostic you want something like (e.srcElement is for IE):
var x = e.target||e.srcElement;
Then get a reference to the element and do what you want:
var refToElement = document.getElementById(x.id);