I am trying to pass a string variable and two arrays to a global function. Something like this:
function send_times_to_device(stop_name, times, headsigns) {
// function code here
}
Later in code:
...
var stop_name = "temp";
var times = new Array(json.length);
var headsigns = new Array(json.length);
...
if(times.length < 6){
send_times_to_device(stop_name, times, headsigns);
}
...
How would I do this correctly in Javascript?
Thanks in advance!
EDIT:
You guys were right, there was an error elsewhere in my code, this works!
new Array(n), creates an array with n undefined entries in it.
If you want to create an array with an integer value as the first entry use :
function send_times_to_device(stop_name, times, headsigns) {
// function code here
console.log(stop_name);
console.log(times);
console.log(headsigns);
}
var stop_name = "temp";
var times = [json.length];
var headsigns = [json.length];
send_times_to_device(stop_name, times, headsigns);
Related
I have a piece of Javascript code that assigns string of values to a string array.
Unfortunately if I try to add more than one string to the array, my UI simulator(which runs on JS code) closes unexpectedly. I have tried debugging but I cannot find anything. I am attaching that piece of code where the issue is. may be you guys could find some flaw? On the pop up button click the values I selcted on the UI should get stored in the array and I have a corressponding variable on the server side to handle this string array.
_popupButtonClick: function (button) {
var solutions = this._stateModel.get('solutionName');
var i;
var solutionsLength = solutions.length;
var selectedSolution = [solutionsLength];
this.clearPopupTimer();
if (button.position === StatusViewModel.ResponseType.Ok) {
for(i=0;i<solutionsLength;i++)
{
if(this._list.listItems[i].selected)
{
selectedSolution[i] = this._list.listItems[i].options.value;
}
}
this._stateModel.save({
selectedsolutions: selectedSolution,
viewResponse: StatusViewModel.ResponseType.Ok
});
} else {
this._stateModel.save({
viewResponse: StatusViewModel.ResponseType.Cancel
});
}
}
Change
var selectedSolution = [solutionsLength];
to
var selectedSolution = [];
This makes your array have an extra item that might be causing a crash.
Also,
you have an
if(this._list.listItems[i].selected)
{
selectedSolution[i] = this._list.listItems[i].options.value;
}
But no corresponding else, so your array has undefined values for i which are not entering the if.
Maybe adding an empty string might solve it:
if(this._list.listItems[i].selected)
{
selectedSolution[i] = this._list.listItems[i].options.value;
}
else
{
selectedSolution[i] = "";
}
The code is looking fine but there seems to be a piece of code which can cause error. For example, you are assigning var selectedSolution = [solutionsLength]; and for example solutionsLength is 5 then your loop runs for 5 times
for(i=0;i<solutionsLength;i++) // runs for 5 times
{
if(this._list.listItems[i].selected)
{
// but selectedSolution = [5]; which is on 0th index and from 1st to 4th index it is undefined
selectedSolution[i] = this._list.listItems[i].options.value;
}
}
So you can try to use push() like
selectedSolution.push(this._list.listItems[i].options.value);
and on initialization change it like,
var selectedSolution = [];
Hopefully this will solve your problem.
var selectedSolution = [solutionsLength];
keeps the value in the selectedSolution variable.
var selectedSolution = [3];
selectedSolution[0] gives the values as 3
So make it simple
var selectedSolution = [];
I'm trying to create an array of objects with an init method, and when I push an object into an array, it should push another object into the array, while keeping track of the length of the array.. The problem is that it doesn't update the length of the array until all the objects have been added, so when each object tries to grab the length, they all get 0.
How can I have it update the length in this process?
here's the jfiddle: http://jsfiddle.net/bg3Vg/13/
As you can see it gives a message showing that the grouptotal is 5, but it seems as if the total counts up from the last pushed object to the first.. I need it to work in the correct order so that the last pushed object can retrieve the correct length.
var colorGroup = [];
var grouptotal = 0;
colorGroup.push(new groupdata(0) );
alert(grouptotal+","+colorGroup[colorGroup.length-1].parent);
function groupdata(parent) {
this.parent = parent;
this.refnum;
this.init = function()
{
grouptotal++;
this.refnum = colorGroup.length;
if(grouptotal<5)colorGroup.push(new groupdata( this.refnum ) );
}
this.init();
}
edit:
ok, I found a way to solve my problem I think. Let me know how horrid this solution is..http://jsfiddle.net/EqAqv/1/
var colorGroup = [];
var grouptotal = 0;
var colorGroupWait = [];
colorGroup.push(new groupdata(0) );
while(colorGroupWait.length>0){
var newcolorGroup = colorGroupWait.shift();
colorGroup.push(new groupdata(newcolorGroup) );
}
alert(grouptotal+","+colorGroup[colorGroup.length-1].parent);
alert(grouptotal+","+colorGroup[colorGroup.length-2].parent);
function groupdata(parent) {
this.parent = parent;
this.refnum;
this.init = function()
{
grouptotal++;
this.refnum = colorGroup.length;
if(colorGroup.length<5)colorGroupWait.unshift( this.refnum );
}
this.init();
}
JavaScript arrays do update the length property as soon as you push something on to them. The problem is that you're recursively calling the constructor, so the statement this.refnum = colorGroup.length is getting executed for each initialization BEFORE any push occurs.
In other words, JavaScript is working as expected.
Is there any particular reason you are doing it in this convoluted manner? It be more straightforward (and achieve the result you're looking for) if you just did it like this:
for(grouptotal=0; grouptotal<5; grouptotal++){
colorGroup.push( new groupdata(grouptotal) );
}
Also, it is convention in JavaScript to name object constructors with a capital letter. So, while groupdata is not invalid syntax, it is confusing: you should consider naming it Groupdata.
#EthanBrown has already pointed out the problems. Here is a solution that puts all the logic in the constructor, and avoids the problem of pushing the instance after having it created from a wrong number.
function GroupData(parentnum) {
this.parentnum = parentnum;
this.refnum = GroupData.colorGroup.length;
GroupData.colorGroup.push(this);
if (GroupData.colorGroup.length < 5)
new GroupData(this.refnum);
}
GroupData.colorGroup = [];
var root = new GroupData(0);
alert(GroupData.colorGroup.length+", "
+GroupData.colorGroup[GroupData.colorGroup.length-1].parentnum);
I know JavaScript passes Objects by reference and thus I'm having a lot of trouble with the following code:
function doGradeAssignmentContent(dtos) {
var x = 5;
var allPages = [];
var stage = new App.UI.PopUpDisplay.PopUpStageAssignmentGrader(null, that);// pass launch element
for(var i = 0; i < dtos[0].result.students.length; ++i) {
var pagesSet = [];
for(var j = 0; j < dtos[0].result.questions.length; ++j) {
var questionObject = jQuery.extend(true, {}, new Object());
questionObject = dtos[0].result.questions[j];
if(dtos[0].result.students[i].answers[j].assignmentQuestionId === questionObject.questionId) {// expected, if not here something is wrong
questionObject.answer = dtos[0].result.students[i].answers[j].studentAnswer;
questionObject.pointsReceived = dtos[0].result.students[i].answers[j].pointsReceived;
} else {
var theAnswer = findAssociatedStudentAnswer(questionObject.questionId, dtos[0].result.students[i].answers[j]);
if(theAnswer !== null) {
questionObject.answer = theAnswer.studentAnswer;
questionObject.pointsReceived = theAnswer.pointsReceived;
} else {
alert("Unexpected error. Please refresh and try again.");
}
}
pagesSet[pagesSet.length] = new App.UI.PopUpDisplay.StageAssignmentGradingPages[dtos[0].result.questions[j].questionType.charAt(0).toUpperCase() + dtos[0].result.questions[j].questionType.slice(1) + "QuestionAssignmentGradingPage"](j + 1, questionObject);
}
var studentInfo = {};
studentInfo.avatar = dtos[0].result.students[i].avatar;
studentInfo.displayName = dtos[0].result.students[i].displayName;
stage.addPageSet(pagesSet, studentInfo);
}
stage.launch();
}
First let me show you what the result (dtos) looks like so you can better understand how this function is parsing it:
The result (dtos) is an Object and looks something like:
dtos Array
dtos[0], static always here
dtos[0].result, static always here
dtos[0].questions Array
dtos[0].questions.index0 - indexN. This describes our Questions, each one is an Object
dtos[0].students Array
dtos[0].students[0]-[n].answers Array. Each student array/Object has an Answers array. Each student will have as many elements in this answers Array that there were questions in dtos[0].questions. Each element is an Object
Now what we do in this here is create this Object stage. Important things here are it has an array called "this.studentsPages". This array will ultimately have as many entries as there were students in dtos[0].students.
So we loop through this for loop disecting the dtos array and creating a pagesSet array. Here comes my problem. On the first iteration through the for loop I create this questionObject element. I also have tried just doing var questionObject = {}, but what you see now was just an attempt to fix the problem I was seeing, but it didn't work either.
So at the end of the first iteration of the outer for loop I call stage.addPageSet, this is what happens here:
var pageObject = [];
pageObject["questions"] = pageSet;
pageObject["displayName"] = studentInfo.displayName;
this.studentsPages[this.studentsPages.length] = pageObject;
if(this.studentsPages.length === 1) {// first time only
for(var i = 0; i < pageSet.length; ++i) {
this.addPage(pageSet[i]);
}
}
The important thing to take notice of here is where I add pageObject on to this.studentsPages which was an empty array before the first call. pageObject now has pageSet plus a little bit more information. Remember, pageSet was an Object and thus passed by reference.
On the next iteration of the for loop, when I hit this line:
questionObject.answer = dtos[0].result.students[i].answers[j].studentAnswer;
It goes wrong. This changes the local copy of questionObject, BUT it also changes the copy of questionObjec that was passed to addPageSet and added to the studentsPages array in the first iteration. So, if I only had 2 students coming in, then when all is said and done, studentsPages hold 2 identical Objects. This should not be true.
The problem is questionObject in the doGradeAssignmentContent function is keeping a reference to the Object created on the previous iteration and then overrides it on all subsequent iterations.
What can I do to fix this?
Thanks for the help!
With out having looked at it too closely I believe you need to change the following:
// Before:
var questionObject = jQuery.extend(true, {}, new Object());
questionObject = dtos[0].result.questions[j];
// After:
var questionObject = jQuery.extend(true, {}, dtos[0].result.questions[j]);
I didn't look too closely if there are other instances in the code where this needs to be applied, but the core concept is to utilize jQuery's deep copy to generate a duplicate of the object you do not wish to retain a reference to.
I was tasked by my professor to make a simple Javascript program that displays simple math problems and their answers in a two dimensional table using a random number. Previously he gave us the example of using a function to write into a table like this:
function RandomGen() {
Random = math.floor(Math.random()*60);
document.writeln("<th>");
document.writeln(Random);
document.writeln("</th>");
}
RandomGen();
In order to use an array, can I do this?
var RandomArray [
RandomGen(),
second_function(),
third_function(),
forth_function(),
]
RandomArray[0];
How do I append the functions together to write into a table?
You almost got it. The correct syntax is:
var randomArray = [
RandomGen,
second_function,
third_function,
forth_function
];
randomArray[0](); // this calls RandomGen
randomArray[1](); // this calls second_function
Remember the basic syntax rules:
A function name with no paranthesis is a function reference. It behaves just like any reference and so can be treated as a variable. Which means you can assign it to another variable, pass it into another function and as the example above stuff it into an array.
Adding paranthesis () to a function reference causes the function to be called. It doesn't matter if the function reference is a plain old function name or stored in another variable or stored in an array.
You can store the function in a variable, then put the variables in an array, and then access them from the array to call them.
var add = function(x,y){ return x + y; };
var multiply = function(x,y){ return x * y; };
var maths = [];
maths.push(add);
maths.push(multiply);
maths[0](1,2);//3
maths[1](3,4);//12
Conversely, you could do this with an object.
var maths = {};
maths.add = function(x,y){ return x + y; };
var four = maths.add(1,3);
Obviously you will have to modify these to match your exact situation.
I want to create a two dimensional array in a javascript function. I found code that should do that but doesn't. I declare the array then define a function to add elements to the array which are also arrays.
// Array function
var card_array = new Array();
function card_array(card_id, card_top, card_left) {
alert('array');
this.card_id = card_id;
this.card_top = card_top;
this.card_left = card_left;
}
// Toggle LinkCard minimize/expand
function toggle_linkcard(toggle, card_id) {
var icard = 0;
$('.linkcard').each(function () {
card_top = $(this).position().top;
card_left = $(this).position().left;
card_i = $(this).attr('id');
card_array[card_array.length++] = new card_array(card_i, card_top, card_left);
icard++;
});
alert(card_array);
}
The line of code where I add elements to the array breaks the code.
card_array[card_array.length++] = new card_array(card_i, card_top, card_left);
What should I fix in that?
You defined the function's name as card_array, same name as the variable's. So after that line of code, you don't have any variable named card_array, only the function. Try changing your variable or function name.
The problem here is that you have two values with the same name: card_array
A variable named which is initialized to a new Array()
A function which takes 3 parameters
The function declaration happens last and hence wins. So when you execute the expression card_array[card_array.length++] you are doing so on a function instance, not an array.
To fix this change the function name to a unique name.
Just change this line:
var card_array = new Array();
into:
var my_card_array = new Array();
And this one:
card_array[card_array.length++] = new card_array(card_i, card_top, card_left);
into:
my_card_array.push(new card_array(card_i, card_top, card_left));
And of course, change the alert.