And I have a function that reads in level data. This is the snippet in question; actors is an array and I'm looping over it until i find an actor of type player.
function Level(plan) {
//Cut snippet..........
this.player = this.actors.filter(function(actor) {
return actor.type == "player";
});
console.log(this.player);
//................
}
The player object,
function Player(pos) {
this.pos = pos
this.size = new Vector(0.8, 1.5);
this.speed = new Vector(0, 0);
}
Player.prototype = new Actor();
Player.prototype.type = "player"
The issue is that in the console, the
console.log(this.player)
will show all the correct details, but when i try to log the position for example
console.log(this.player.pos)
I get undefined. Its a simple program, I'm not using ajax or anything. Thought it might be do with execution order, can someone explain this to me and a solution? If it is todo with execution order, an explanation would be much appreciated.
Thank you very much,
Rainy
You get undefined because when you filter your actor array, you get a new array as a result. So console.log(this.player) outputs an array, not a single object.
You need to get the first element of the array this.player to output its pos property.
Something like this:
if(this.player.length > 0)
console.log(this.player[0].pos);
Use reduce instead of filter for a single player.
this.player = this.actors.reduce(function(current, actor) {
return actor.type === 'player' ? actor : current;
});
Related
So I have a class that looks something like this:
class Car {
constructor(name, pos) {
this.carName = name;
this.carPos = pos;
}
}
I then end up creating an array of objects using this class as so:
newCar = new Car("Fusion","100 100");
let carManifest = [newCar]
I later in my code go on to carManifest.push() several other Car objects into the array, building it up. Eventually I run into a for loop such that:
for (index = 0; index < carManifest.length; index++) {
if(carManifest[index].carName === 'Honda')
<Do Stuff>
}
Whenever I go to access carManifest[index].carName I get "undefined". I also had a get method within the object for the same variable, but using that in this context wouldn't even compile. I am aware that the array itself does not have these variables, but as far as I'm aware there is no way to declare an array to be of a specific class in JS like you can in Java and C.
Could anyone help me out? I am new to JS and have been stumped on this for the past hour. I will be glad to update this if there is not enough info. Thanks!
Note: Not sure if it matters but I am using Node.js
Change your code from
let carManifest = [newCar]
to push item to array as
carManifest.push(newCar);
/*
function Car (name, pos) {
this.carName = name;
this.carPos = pos;
}
*/
class Car {
constructor(name, pos) {
this.carName = name;
this.carPos = pos;
}
}
newCar = new Car("Fusion","100 100");
let carManifest = [];
carManifest.push(newCar);
for (index = 0; index < carManifest.length; index++) {
if(carManifest[index].carName === 'Fusion'){
console.log(carManifest[index].carName);
}
}
Are you pushing other variables or objects into the same array? There is nothing wrong with the code examples you're showing, you are able to access the variables of the objects this way. You'll have to show more code, where exactly are you getting undefined?
I'm pushing an object into an array of objects. One of the properties of the object (which is an array) is showing up as undefined, after the object is pushed to the array. If you look at my code below, where it says, "WHY IS THIS SHOWING IN CONSOLE?" - it doesn't make sense because if the array is undefined, it should have been undefined in both of the previous two checks (where it says "THIS IS NOT SHOWING IN CONSOLE."). This is driving me crazy. SOS. Please help.
var pathCopy = unit.path; // THIS IS AN ARRAY AND IT IS NOT EMPY
var directionCopy = unit.direction;
if (pathCopy.length < 1) {
console.log('THIS IS NOT SHOWING IN CONSOLE');
}
var object = {
'type': 'move',
'time': gameTime,
'name': unit.name,
'vector': pathCopy,
'direction': directionCopy
};
currentGameEvents.push(object);
if (object.vector.length < 1) {
console.log('THIS IS NOT SHOWING IN CONSOLE');
}
for (var i = 0; i < currentGameEvents.length; i++) {
if (currentGameEvents[i].vector.length < 1) {
console.log('WHY IS THIS SHOWING IN CONSOLE??');
}
}
I’m not sure how or why, but your example works, if I insert the undefined variables (i.e. I replaced unit.path with [345,34623,52] or something that is an array literal).
The only difference to that is, that you actually assign the reference to that array, instead of declaring a new array.
var pathCopy = unit.path; // pathCopy and unit.path are the SAME array
var pathCopy = [345,346,345]; // pathCopy is a completely NEW array
To fix this, try something like
var pathCopy = unit.path.slice(); // pathCopy is a completely NEW array that contains the same values as unit.path
whenever you want to copy an array; add .slice() at the end!
Again, this is deducing from the only difference between your code and what I tried, and this is probably the reason, why your code doesn’t work.
Another assumption is that currentGameEvents is an Array. Your code wouldn’t work at all, otherwise. I’m mentioning this because the title states that you were trying to push to an object, which isn’t possible.
function addNumifnotThere(numer){
var numCent = [];
numCent.forEach(function(){
if(numer in numCent)
console.log("you logged that");
else
numCent.push(numer);
});
return numCent;
}
This is my current code, what its attempting to do is read an array and if there is already an element exits the loop and says "you already logged that", obviously if it cannot find a similar element then it pushes it to the array.
I want this to work dynamically so we cannot know the size of the array beforehand, so the first element passed as an argument should be put into the array, (addNum(1) should have the array print out [1], calling addNum(1) again should print "you already logged that")
However there are two problems with this
1) Trying to push to a new array without any entries means everything is undefined and therefore trying to traverse the array just causes the program to print [].
2) Adding some random elements to the array just to make it work, in this case numCent=[1,2,3] has other issues, mainly that adding a number above 3 causes the code to print incorrect information. In this case addNum(5) should print [1,2,3,5] but instead prints [1,2,3,5,5,5]
I know this has to be a simple mistake but I've been dragging myself too long to not ask for help.
EDIT: Thanks to the many outstanding answers here I have now leanred about the indexOf method, thank you guys so much.
For every non-match you are pushing the number. Use something like this
var numCent = [];
function addNumifnotThere(numer)
{
var index = numCent.indexOf(number);
if(index >=0)
{
console.log("you logged that");
}
else
{
numCent.push(number);
}
return numCent;
}
Use Array.prototype.indexOf
var numCent = [];
function addNum(numer){
if (numCent.indexOf(numer) > -1)
{
console.log("Number already in array");
}
else
{
numCent.push(numer);
}
}
//DEMO CODE, not part of solution
document.querySelector("button").addEventListener("click", function(){
if (document.querySelector("input").value.length > 0)
{
addNum(document.querySelector("input").value);
document.querySelector("div").innerHTML = numCent.join(", ");
}
}, false);
Output
<div id="output"></div>
<input />
<button>Add number</button>
indexOf tests if an element is inside the array and returns its index. If not found it will return -1. You can test for this. You can try it for your self in this snippet. It will only allow you to add a number (or any string, in this example) once.
I also was confused by the newCent array declaration inside the function. I think, based upon the content of your question, you meant this.
If you want the array held in the instance, you can do it like this.
function AddIf(arr){
if( arr || !this.arr ) {
this.arr = arr || [];
}
return function(number) {
if( this.arr.indexOf(number) >= 0 ) {
console.log("Already Present!");
} else {
this.arr.push(number);
}
return this.arr;
}.bind(this);
}
// Usage would be like this:
// var addIf = new AddIf([1, 2, 3]);
// addIf(10); // returns [1, 2, 3, 10]
// addIf(10); // logs "Already Present!", doesn't add 10 to array
This basically returns a function, with this bound to the function being called. If you pass in an initial array, it will use that array to compare to when adding it to the array.
You can catch the return function and call it as you would want to. If you don't call new when invoking however, it will share the same array instance (and have a funky way of being called, AddIf()(10)).
I used fn.bind() to ensure the function gets called in the correct context every time, if you were wondering why I called it like that.
Do do this cleanly, I'd consider prototyping the global Array object and adding a method to push values but only if they're unique to the array. Something like this:
Array.prototype.pushUnique = function (item) {
if (this.indexOf(item) != -1) {
console.log("Item with value of " + item + " already exists in the array."
}
else {
this.push(item);
}
}
If you're not comfortable prototypeing global types like Array, you can build the same thing in a procedural pattern:
function arrayPushUnique (arr, item) {
if (arr.indexOf(item) != -1) {
console.log("Item with value of " + item + " already exists in the array."
}
else {
arr.push(item);
}
}
Then to use it, simply create a new empty array and start pushing things to it.
var numCent = [];
// The Array.prototype method
numCent.pushUnique(number);
// The procedural method
arrayPushUnique(numCent, number);
I have a list of objects as shown in the image.
These all have the property statusCode: 62467 but the journey property goes like: 0,1,2,3,3,4,4,4,4
I want to loop through these objects and return the FIRST of the duplicated (they are not the same object, just that both have the same journey number and the same status code) objects with the same journey number.
So I want to return the bold objects: 0,1,2,3,3,4,4,4,4
$.each(points, function (index, point) {
for (i = 0; i < journeyNumber.length; i++) {
if (point.k.journey === journeyNumber[i] && point.k.statusCode === '62467') {
console.log(point);
latlngs.push(point.j.aa.k);
latlngs.push(point.j.aa.B);
}
}
});
The screenshot is the log of console.log(point), so ideally I would like another loop inside which returns only the first object of the same journey number.
Hope this makes sense and thank you for your time.
Try this,
var temp = [];
$.each(points, function (index, point) {
if (temp.indexOf(point.k.journey) === -1) {
temp.push(point.k.journey);
console.log(point);
latlngs.push(point.j.aa.k);
latlngs.push(point.j.aa.B);
}
});
Create a fresh object with status codes and check against that.
var journeys = {};
for(object in points){
// extract the properties you want (or use them directly, this is not necessary)
var journey = points[object].journey;
var status = points[object].statusCode;
// use the typeof operator to see if the journey has already been set before
if(typeof journeys[journey] == "undefined"){
// then define it.
journeys[journey] = status;
}
}
(Please note I am not actually correctly referencing the journey and statusCode, you'd have to do something like objects[object][k].journey to access the right property, but thats not really the point)
You can even add anything you want into the journeys object, nesting another object with the extracted latitude and longitude, or even just nesting the entire object in the journey!
journeys[journey] = points[object];
Now you can get every journey by looping through them again, and the associated first statusCode:
for(journey in journeys){
console.log("First instance of journey " + journey + " had statusCode " + journeys[journey]);
}
i am trying for the first time to implement OOP in javascript and i got stuck on a recursive function when i try to send an array of objects to this function. So, i have the "Pitic" class (pitic means midget in romanian) with some propreties:
function Pitic(piticID) {
this.id = piticID;
this.inaltime = null;
this.greutate = null;
this.genereazaGreutate();
this.genereazaInaltime();
}
I'm now generating some midgets and storing them in the public piticiCollection Array variable. The "genereazaGreutate" and "genereazaInaltime" are function to generate random values for the inaltime and greutate values.
var pitic = new Pitic(idPitic);
piticiCollection.push(pitic);
The problem appears when i try to send the array of midgets to a function because all i get is only the first item of the array.
So, before i call the function, i have piticiCollection array with 4 objects:
midgets are safe and sound http://img443.imageshack.us/img443/484/yr4f.png
And as soon as i call the function with the piticiCollection as a parameter i loose 3 midgets! :(
most of the midgets are gone http://img201.imageshack.us/img201/5808/7od5.png
p.s. please excuse me for my bad english..
[EDIT]
Here is a fiddle of my full code: http://jsfiddle.net/WT7Ud/ I call the function on line 56 and as soon as the debugger hits line 60 i loose array items.
I have solved my problem by creating a copy of the array before using it in the function. Strange :(
function determinaPerechi(somePitici) {
var piticDeComparat, colectieDePiticiCopy;
colectieDePiticiCopy = somePitici;
for (var i = 1; i < colectieDePiticiCopy.length; i++) {
var piticDeComparat2 = null;
piticDeComparat = colectieDePiticiCopy[0];
piticDeComparat2 = colectieDePiticiCopy[i];
if (piticDeComparat.inaltime < piticDeComparat2.inaltime) {
//Perechea poate fi prietena
}
}
//colectieDePiticiCopy.splice(0, 1);
if (colectieDePiticiCopy.length == 0) {
//alert("finish");
return;
}
determinaPerechi(colectieDePiticiCopy);
//test(ttt);
}
Your determinaPerechiPosibile is modifying the original array on this line:
colectieDePitici.splice(1, colectieDePitici.length);
In particular, it is removing all but the first element. You probably should be using slice to non-destructively extract the part of the array you want to recurse on.
As Ted Hopp mentioned, the problem appears to be the line
colectieDePitici.splice(1, colectieDePitici.length);
in combination with this line:
determinaPerechiPosibile(colectieDePiticiCopy);
If those two lines are commented out, the array maintains its original length.