Before reading below, do note that I have only recently started learning Javascript.
I am interested in making a text-based survival game. When trying to subtract a random number of survivors from the whole, I attempted to write what I think is, "A raid happens if the number is 0.50 - 1.00, and if the raid is successful, the group loses a random number of survivors between 1, and however many survivors there are." However, when I write this, I get an ESLint error, stating: ERROR: Parsing error: Unexpected Token if I don't know how I would rewrite it, or how to reformat it to work, if it is at all possible. The issue is in the code below, on lines 10, 11, & 12.
//constants
var EVENT_CHANCE = 0.15;
var EVENT_TYPE = 0.50;
var FOOD_CONSUMPTION = FOOD_CONSUMPTION;
var MATERIALS_CONSUMPTION = 1;
var ENEMY_STRENGTH = 10;
var SURVIVOR_STRENGTH = 1;
//equations
this.FOOD_CONSUMPTION = (this.food - this.surviors);
this.raid = if ( EVENT_TYPE > 0.50);{
this.survivors - Math.floor((Math.random() * this.surviors) + 1);
};
Let me know if I left anything important out
Note: I copied this post from the game development stack exchange, because they had advised me it is more of a stack overflow question, as it relates more to JS as a whole, than game development.
You have a semicolon after the condition
To conditionally assign a variable you need to use the ternary operator, for example:
const thing = condition ? ifTrue : ifFalse;
Or for your code:
this.raid = EVENT_TYPE > 0.50 ?
this.survivors - Math.floor((Math.random() * this.surviors) + 1) :
null;
//replace the null with what you want the variable to be if the condition is false
You can't use a statement as the right-hand side of an assignment, which is what you're trying to do here:
this.raid = if ( EVENT_TYPE > 0.50);{
this.survivors - Math.floor((Math.random() * this.surviors) + 1);
};
If you want to set this.raid to the result of EVENT_TYPE > 0.50, you just do that directly:
this.raid = EVENT_TYPE > 0.50;
If you then want to use that in a branch, you can follow it with the if testing this.raid:
this.raid = EVENT_TYPE > 0.50;
if (this.raid) {
this.survivors - Math.floor((Math.random() * this.survivors) + 1);
}
(I also fixed a typo in that, the second survivors was missing a v. But there's still a problem I didn't know how to fix: It calculates a value without storing it anywhere. It's not an error in JavaScript, but it probably isn't what you wanted. You may have meant -= instead of -.)
Note that neither of the ; that were originally in that if belonged there. You don't put ; after the () in an if, and you don't put a ; after the block attached to a flow-control statement (if, while, etc.).
Related
I am trying to calculate an angle in js using math js. I am experienced that when the division is between negative numbers js give me bad results. e.g. -6/-3 give me 20093 instead of 2.
How can I solve this? here below you can see a portion of console.log.
Here is the code:
var num = math.eval(parseInt(p[1]) - parseInt(d3.event.y));
var den = math.eval(parseInt(p[0]) - parseInt(d3.event.x));
if (den==0){
var angle = 0;
}else{
var m = math.eval(num/den);
if(m<1){
theta = m*100;
}else{
theta = m*100;
}
}
Syntax in code is num/den as you can see.
Thanks in advance
You can simply do -6/-3.
Run this in your developer tools console: alert(-6/-3); and you will see.
I think math.eval() expects a string like "-6/-3".
I'm not sure how to word the question and i'm still quite new at javascript.
So I've got a random quote generator that has each quote result as an array. I'd like to add in two items in the array which I've got so far but having one result be a random number generated eg "2 quote" but having 2 be randomised each time. The end result is for a browser based text game. So it could be "2 zombies attack" or "7 zombies attack." The code I have so far is:
var quotes = [
[x, 'Zombies attack!'],
[x, 'other creatures attack'],
['next line'],
]
function newQuote() {
var randomNumber = Math.floor(Math.random() * (quotes.length));
document.getElementById('quote').innerHTML = quotes[randomNumber];
}
Ideally need x(or i however it's going to work) to be the result of a random number between a set range, each differently each array.
Thank you
p.s I forgot to mention that not all the quotes require a number. Thats why I've done it as a double array.
If I understand your goal correctly, you want to have a set of similar-ish message templates, pick one of them at some point and fill it with data, correct? There's a lot of ways to tackle this problem, depending on how varying can your templates be. For a simple case in my head where you just need to prepend a number to a string I'd do something like this:
var messages = [" zombies attack",
" other creatures attack"], // define your messages
messageIndex = Math.floor(Math.random() * messages.length), // pick one of them
numberOfMonsters = Math.floor(Math.random() * 10 + 1), // get your random number
result = numberOfMonsters + messages[messageIndex]; // construct a resulting message
document.getElementById('quote').textContent = result;
If you'd rather have more complex strings where you don't necessarily add a number (or any string) to the beginning, like ["There's X things in the distance", "X things are somewhere close"], then I'd recommend to either come up with some sort of string formatting of your own or use a library to do that for you. sprintf.js seems to be just right for that, it will let you do things like this:
var messages = ["%d zombies attack",
"A boss with %d minions attacks"], // define your messages
messageIndex = Math.floor(Math.random() * messages.length), // pick one of them
numberOfMonsters = Math.floor(Math.random() * 10 + 1), // get your random number
result = sprintf(messages[messageIndex], numberOfMonsters) // format a final message
document.getElementById('quote').textContent = result;
EDIT: Your task is much more complex than what is described in the original question. You need to think about you code and data organization. You have to outline what is finite and can be enumerated (types of actions are finite: you can loot, fight, move, etc.), and what is arbitrary and dynamic (list of monsters and loot table are arbitrary, you have no idea what type and amount of monsters game designers will come up with). After you've defined your structure you can come up with some quick and dirty message composer, which takes arbitrary entities and puts them into finite amount of contexts, or something. Again, I'm sort of shooting in the dark here, but here's an updated version of the code on plunkr.
I solved it to do what I want and still have the numbers different. The issue was I should have had the number generator within the quote function. Also can create multiple variables to use too for different number generators. The plan is to then integrate it with php to add content dynamically. Which I can do. Thanks Dmitry for guiding me in the right direction.
function newQuote() {
var MonsterOne = Math.floor((Math.random() * 14) + 0);
var MonsterTwo = Math.floor((Math.random() * 14) + 0);
var MonsterThree = Math.floor((Math.random() * 14) + 0);
var MonsterFour = Math.floor((Math.random() * 14) + 0);
var quotes = [
['Test', MonsterOne, 'One'],
['Test', MonsterOne,'Two'],
['Test', MonsterThree, 'Three'],
[MonsterFour, 'Four'],
['Five'],
]
var randomNumber = Math.floor(Math.random() * (quotes.length));
document.getElementById('quote').innerHTML = quotes[randomNumber];
}
I've already looked at quite a few other questions but I can't seem to fix this issue with setTimeout
So I've been working on this and came to this, but for some reason the setTimeout does not work, any tips?
function curves(val_name, mini, maxi, t_amount, steps) {
//t_amount MUST be in ms
for (x = 0; x < steps; x++) {
var x_mod = scale(x, -6, 0, 0, steps);
var value = setTimeout(calculate_curve, (t_amount / steps), x_mod);
switch (val_name) {
case "vol_stretch1":
var vol_stretch1 = this.patcher.getnamed("stretching").subpatcher(0).getnamed("vol_stretch1");
vol_stretch1 = value
break;
case "vol_stretch2":
var vol_stretch2 = this.patcher.getnamed("stretching").subpatcher(0).getnamed("vol_stretch2");
vol_stretch2 = value
break;
case "vol_stretch3":
var vol_stretch3 = this.patcher.getnamed("stretching").subpatcher(0).getnamed("vol_stretch3");
vol_stretch3 = value
break;
}
}
}
function calculate_curve(x) {
var constant_e = 2.718281828459;
var result = (1 / 1 + (constant_e ^ (x * -1))) * -1; //sigmoid function * -1 to have the nice rise
}
function scale(unscaledNum, minAllowed, maxAllowed, minimum, maximum) {
return (maxAllowed - minAllowed) * (unscaledNum - minimum) / (maximum - minimum) + minAllowed;
}
You can ignore the switch as it works with an extension for MaxMSP but isn't very important here. The error I get back is "Javascript ReferenceError: setTimeout is not defined". Any help is greatly appreciated!
I've not worked with Max before, but from a small amount of searching it looks like you're writing something along the lines of a plugin.
It looks like Max is running it's own Javascript environment of some sort. setTimeout is a method on the window object of browsers in Javascript, and as such it is not necessarily implemented in Javascript outside of the browser, as Max appears to be.
The recommended alternative seems to be to use the Task object exposed by the environment, which has some documentation here:
https://docs.cycling74.com/max5/vignettes/js/jstaskobject.html
I have no way of testing this, but from the documentation it looks like something along the lines of the below should work:
var task = new Task(function() {
calculate_curve(x_mod);
}, this);
task.schedule((t_amount / steps));
Allright, I know what machine precision is, but this, I can't understand...
Code:
console.log("meanX",meanX);
meanX2 = meanX * meanX; //squared
console.log("meanX2",meanX2);
Console output:
meanX 300.3
meanX2 28493.4400000000002
In case you are wondering, the correct value for meanX2 would be 90180.09
And this is only one of the many examples visible in the screenshot..
.toFixed(6) seems to fix this... But I have no idea why it doesn't work without it.
Edit
Ok, I don't want to post the whole program code here because in first place I'm not the only author, and second, I also wouldn't like this to be copied without our permission. But I'll gladly explain how I get this error and will post the whole method/function code here.
This code belongs, as you may have guessed from the window title, to a lane detection algorithm. We use Three.js/webgl to run some pre processing shaders on each frame of a video and then we analyze the resulting image. The method/function you see on the screenshot is a perpendicular line fitting algorithm and is part of the whole thing.
I can see the algorithm running nicely because I have the lane being drawn on top of the video, and It is well placed. Until suddenly the lane turns into an horizontal bar. This unexpected behavior happens exactly because of the phenomenon I described here, since it's from that moment that I start to see wrong math in the console.
Also, because the video and algorithm run at slightly different fps everytime, the problem doesn't always happen in the same moment of the video, and sometimes It doesn't happen at all.
Here is the code (it has some alterations because I was trying to isolate the issue):
this.perpendicularLineFit = function (points, slopeSign) {
var count = points.length;
var sumX = 0,
sumY = 0;
var sumX2 = 0,
sumY2 = 0,
sumXY = 0;
var meanX, meanY;
var i, lowp = {}, highp = {};
var B;
var slope;
var originY;
for (i = 0; i < count; i++) {
sumX += points[i].x;
sumY += points[i].y;
sumX2 += points[i].x * points[i].x;
sumY2 += points[i].y * points[i].y;
sumXY += points[i].y * points[i].x;
}
meanX = sumX / count;
meanY = sumY / count;
//If you uncoment this, problem reappears:
//var numeratorLeft = meanY * meanY;
console.log("meanX",meanX);
var meanX2 = meanX*meanX;
console.log("meanX2",meanX2);
var numerator = (sumY2 - count * (meanY * meanY)) - (sumX2 - count * meanX2);
var denominator = (count * meanX * meanY - sumXY);
B = 0.5 * (numerator / denominator);
slope = -B + slopeSign * Math.sqrt(B * B + 1);
originY = meanY - slope * meanX;
slope = isNaN(slope) ? slopeSign : slope;
originY = isNaN(originY) ? originY : originY;
lowp.y = this.lowY;
lowp.x = (this.lowY - originY) / slope;
highp.y = this.highY;
highp.x = (this.highY - originY) / slope;
return {
low: lowp,
high: highp
};
};
Now, I was trying to understand what was causing this, and the most bizarre thing is that it seems that when I place a statement of this form
var x = ... meanY * meanY ...;
before the meanX2 attribution, the issue happens. Otherwise it doesn't.
Also, I tried to catch this anomaly in the debugger but just when I enter the debugging tab, the problem disapears. And the values turn correct again.
I certainly don't believe in black magic, and I know that you are probably skeptic to this.
I would be too. But here is a link to a video showing it happening:
The video
Edit2:
I managed to reproduce this issue in another computer.. Both having ubuntu and using firefox (versions 20 and 21).
Edit3:
I'm sorry it took so much time! Here is a zip containing the issue. Just run it in any webserver. The code mentioned is in LaneDetection.js. Search for "HERE" in the file to find it.
https://docs.google.com/file/d/0B7y9wWiGlcYnYlo1S2pBelR1cHM/edit?usp=sharing
The problem might not happen in the first attempts. If that's the case refresh the page and try again. When the lines get horizontal you know it's there. As I said, I saw this problem happening in firefox versions 20 and 21 on ubuntu. In chrome it never happened.
By the way, I noticed that changing javascript.options.typeinference flag in firefox seems to stop the problem... I don't know exactly what that flag does, but maybe this optimization is not correctly implemented in firefox?
I can't say for sure that I actually have an answer but I think that I have confirmed that basilikum was correct to suggest a memory problem. Here's what I did: I took the first ten entries from your screenshot and calculated the correct answer. I then converted the correct answer and the wrong answer into the hexidecimal representation of the double-precision float. What I ended up with was the following:
292.416^2 = 85507.506 = 40F4E0381C71C71E
changed to 27583.373 = 40DAEFEB1C71C722
293.166^2 = 85946.694 = 40F4FBAB1C71C72A
changed to 27583.373 = 40DAEFEB1C71C722
295.818^2 = 87508.396 = 40F55D4658DC0876
changed to 28041.024 = 40DB62419637021F
294.500^2 = 86730.250 = 40F52CA400000000
changed to 27583.373 = 40DAEFEB1C71C722
297.000^2 = 88290.000 = 40F58E2000000000
changed to 28041.024 = 40DB62419637021F
221.750^2 = 49173.062 = 40E802A200000000
changed to 24964.000 = 40D8610000000000
300.300^2 = 90180.090 = 40F6044170A3D70A
changed to 28493.440 = 40DBD35C28F5C290
220.200^2 = 48488.040 = 40E7AD0147AE147B
changed to 25408.360 = 40D8D0170A3D70A4
300.600^2 = 90360.360 = 40F60F85C28F5C29
changed to 28493.440 = 40DBD35C28F5C290
213.000^2 = 45369.000 = 40E6272000000000
changed to 28032.326 = 40DB6014E5E0A72E
There's no persistent pattern to the change but there are a couple instances that are very telling of a memory issue. In the first two entries you can see that bytes 1, 2 and 3 were unchanged. In the 9th entry there's something even more odd. It would appear that bytes 0 - 3 were shifted left by exactly 4 bits! Upon considering the statement that the problem doesn't arise until after some time has passed and in light of these two anomalies, I'm fairly confident that you're encountering some sort of memory issue. Could it be, dare I say, a stack overflow?
I am having a problem with a simple script that is supposed to update a page with some values(user input) that are turned from monthly to yearly (the numbers go into numeric fields created by confirmIT)
<script>
function update() {
for (var i = 0; i < 9; i++) {
var ans = parseInt(document.getElementById("bq10a_" + i).value, 10);
if (!isNaN(ans)) {
var new = ans * 12;
document.getElementById("bq10a_" + i + "calc").value = new;
}
}
}
return;
}
setInterval("update()", 1000);
</script>
this yields an Expected identifier error on line
var new = ans*12;
and i would appreciate any help on how to solve it
The word new is a reserved word in JavaScript and cannot be used as the name of a variable.
The error means that the parser expected an "identifier", which is to say that it expected to see a valid identifier.
Change the name of the variable and things should improve. In the code you've posted I think there's a { } nesting problem; there appears to be one too many before the return of the function.
edit — also as jbabey notes in a comment, your setInterval() call should be
setInterval(update, 1000);
It's not a good idea, generally, to pass strings to setInterval(), despite the advice of thousands of mouldy old instructional websites.
Word "new" -- is special in javascript language:
line is incorrect:
var new = ans*12;
try this:
var newvalue = ans*12;
More information on:
http://javascript.about.com/library/blreserved.htm
http://www.ecma-international.org/publications/standards/Ecma-262.htm