I trying to make a small text based rpg game, but I came across array in js and then I came to problems, I failing to increase the index number by using i instead of 0 like myArray[i]
I made a jsfiddle so you guys can see what I mean.
jsfiddle
When you press the button til you get a warming, it should increase the i to 2, but it don't, but still comes with warming and increasing the attack variable.
This is your attackUp function:
function attackUp(){
var i = 0;
var attackCost = xpforlevel[i];
if (attackCost < attackxp) {
alert("WARMING!");
attack++;
document.getElementById('attack').innerHTML = attack;
i++;
document.getElementById('i').innerHTML = i;
}
}
Notice that your var i = 0 statement doesn't really make sense (because everytime attackUp is called, i will be reset to = 0 at the beginning). To fix that, erase this var i = 0 statement from your function and put in the beginning of your JS code:
var i = 0;
var attackxp = 0;
var attack = 1;
Further, your function will only update i if attackCost < attackxp, otherwise it will change nothing. You need to put the i++; statement outside your if-block, like this:
function attackUp(){
//erase this line: var i = 0;
var attackCost = xpforlevel[i];
i++; //added this line
if (attackCost < attackxp) {
alert("WARMING!");
attack++;
document.getElementById('attack').innerHTML = attack;
//erase this line: i++;
document.getElementById('i').innerHTML = i;
}
}
As your i is a local variable, it is initiated as 0 every time you call attackUp(). You should put it besides attackxp and attack.
For more information about the scope of variable in JavaScript, see w3schools or this question.
Related
I want to make a program in javascript in which a person inputted the iteration count for a for loop(they could input x++, or y--), but I don't know if I am using the right method.
Here is my code:
var x = prompt("iteration count")
// x should equal something like, i++, or x--
for(var i = 0; i < 10; x){
document.write(i)
}
But when the code ran the program kept crashing.
Why is it crashing and how do I fix this?
Please Help
you need to parse the int value of x because it's a string and use it to increment i
var x = parseInt(prompt("iteration count"))
for (var i = 0; i < 10; i += x) {
document.write(i)
}
EDIT :
based on the question edit and the comments, you can use eval(), but :
Do not ever use eval!
eval() is a dangerous function, which executes the code it's passed with the privileges of the caller.
So before you use it, read the MDN page and check : eval isnt evil it's just misunderstood
where there's this comment from Spudley :
From a security perspective, eval() is far more dangerous in a server
environment, where code is expected to be fully trusted and hidden
from the end user.
In a browser, the user could eval any code they wanted at any time
simply by opening dev tools, so as a developer you can't get away with
having anything on your client code that could be insecure against
eval anyway.
to test the snippet below, type i++ in the prompt
var x = prompt("iteration count");
for (var i = 0; i < 10; eval(x)) {
console.log(i)
}
an alternative to eval() would be new Function or check the answers here : Programatically setting third statement of for loop
var input = 'i++';//Or whatever condition user passing in
var conditionProgramatically = () => new Function(input)() ;
for (var i = 0; i < 10; conditionProgramatically()) {
console.log(i)
}
For for-loop, third statement will be invoked/executed on every iteration, and hence we set a function call, and in that function, we execute whatever user passing in as you've mentioned i++
That is an endless loop because the variable i never incremented. Try this one.
var x = prompt("iteration count")
for(var i = 0; i < x, i++){
document.write(i)
}
You forgot to increment the index variable, it result to endless loop and maximum stack error, you can also use + for parseInt shorcut.
var x = +prompt("iteration count")
for(var i = 0; i < x;i++){
document.write(i)
}
You have to parse the input value and then make it as a condition to stop iterating after the given value.
var x = parseInt(prompt("iteration count"))
for (var i = 0; i < x; i++) {
document.write(i);
}
I have homework and these are my instructions:
create javascript 06.js with a general function: addThemUp()
There is NO HTML page. There is NO EVENT HANDLER.
The function receives two parameters. They go between (..).
Use any names you want for the parameters but you could use descriptive names
Add all integers from the first parameter to the second.
All you need to do is use a for() loop and return the total.
Return the total of the integers. Use return because this is a general function.
Here is my code
function addThemUp(earlier,later) {
var total = 0;
for (i = 0; i <= earlier; i ++) {
total = total + 0;
};
return total;
};
For some reason this one is messing up bad. We were able to do this exact same thing with Count but adding up and array seems to be different. When I run it through the grader I'm only receiving 25% grade.
You need to make use of both earlier and later in your loop:
function addThemUp(earlier,later) {
var total = 0;
for (i = earlier; i <= later; i ++) {
total = total + i;
};
return total;
};
Shouldn't it be using
i <= later
As it would stop on the first value otherwise?
I'll point out two things that could help you on your way.
First: this line
total = total + 0;
Think about what it's doing for a bit.
total (which starts as 0) is adding... 0... to itself. ;)
Next, this line:
for (i = 0; i <= earlier; i ++) {
IIRC, earlier is the first of the two numbers you're concerned about.
That part of the for loop says "stop when this condition is met." ;)
I'm making a typing game. When multiple players play the game it runs through the same set of functions again. I'm using the variable j as a counter to advance words when they are typed correctly. For some reason, on the second pass on each upkeystroke, it logs j = 1 & j = whatever the value of the previous players last word + 1 is. When each player plays, I want each set of words they are typing to be the same, so that it is fair. I can't figure out why this is happening or even how the variable has 2 values at the same time?!?!?
What gives?
Here's the code in question, but there's a bunch of callbacks that could be involved, although the only place this variable is called is inside this function.
//advances ship on correct typing
function runRace() {
timer();
var j = 1;
//BUG HERE !! Works fine on first iteration but on second
//iterations value jumps beteween 1 and whatever the next
//one is. It's like on every keystroke it reassigns var j
//back to 1, then back to the element number it was on
//last time
//!!! j has 2 values !!!it's keeping the value from the
//prior running of run race
$(document).keyup(function(e){
var targetWord = $(".toType").text();
var typedWord = $("#word").val();
//while (j < gameWords.length){
console.log("j = " + j);
if(typedWord === targetWord){
$(".player").css({left: "+=15px",});
targetWord = $(".toType").text(gameWords[j]);
$("#word").val("");
j++;
}else {
return
};
//}
});
}
If you need to see the rest of the code to figure this out, it's here. Eventhough it's not running right on jsfiddle for reason, it works other then the bug, locally https://jsfiddle.net/ujsr139r/1/
As i mentioned in my comment you're creating multiple listeners everytime runRace() is called.
You could try something like this instead (please note, this isn't the best way to do this, i'm just demoing. Global variables like j in this case aren't a clever idea.:
var j=1; // global because its outside of your function
$(function(){
$(document).keyup(function(e){
var targetWord = $(".toType").text();
var typedWord = $("#word").val();
//while (j < gameWords.length){
console.log("j = " + j);
if(typedWord === targetWord){
$(".player").css({left: "+=15px",});
targetWord = $(".toType").text(gameWords[j]);
$("#word").val("");
j++;
}else {
return
};
//}
});
});
//advances ship on correct typing
function runRace() {
j = 1;
timer();
}
I'm trying to implement Heap's algorithm to find different permutations of a string and found a strange behaviour with a for loop, here's the code
function permAlone(str) {
var strArr = str.split(''),
permutations = [];
function swap(strArr, x, y) {
var tmp = strArr[x];
strArr[x] = strArr[y];
strArr[y] = tmp;
}
function generate(n) {
if (n === 1) {
permutations.push(strArr.join());
} else {
for (var i = 0; i != n; i++) {
generate(n - 1);
swap(n % 2 ? 0 : i, n - 1);
}
}
}
generate(strArr.length);
return permutations;
}
console.log(permAlone('aab'));
In the for loop within the generate function, if I put i = 0 the output of the script is ['a,a,b', 'a,a,b'] but if I put var i = 0 the output is ['a,a,b', 'a,a,b', 'a,a,b', 'a,a,b', 'a,a,b', 'a,a,b'].
I understand that var i would create a local variable for the loop, but don't understand in this case why it would change how the loop functions as there is no i variable declared anywhere else in the script.
Thanks any help appreciated.
The reason the behaviour changes if you have a global i variable is that you have multiple recursive calls to generate() all trying to control their own partially complete for loops with the same variable, and all setting i back to 0 when they start.
Picture what happens on the second iteration of the for loop: i is 1 because it has just been incremented, but then immediately a recursive call to generate() starts its own loop and sets i back to 0 again.
If you create a local variable with var then each for loop in each recursive call is independent of all the others.
Try stepping through the code with the debugger, or try adding the following as the first line inside the for loop and watch what happens to the variables when the code runs:
console.log('n:' + n + '; i: '+i);
i'm new to javascript and i'm having a problem. I want the actual (function updateBoxes) box [boxIx] to be bigger than the other ones but i can't seem to find a code that works. i've tried box[boxIx].size ="100px"; box[boxIx].style.size ="100px"; without result. This is my code;
function init() {
box = document.getElementById("boxes").getElementsByTagName("div");
for (var i=0; i<box.length; i++) {
box[i].style.left = 70*i+"px";
} // End for
boxIx = box.length - 8;
updateBoxes();
} // End init
function browseLeft() {
if (boxIx > 0) boxIx = boxIx - 1;
updateBoxes();
}
// End browseLeft
function browseRight() {
if (boxIx < box.length-1) boxIx = boxIx + 1;
updateBoxes();}
// End browseRight
**function updateBoxes() {
box[boxIx].style.backgroundColor ="#CCC";
box[boxIx].style.top = "20px";
box[boxIx].style.zIndex = 9;**
var z = 8;
for (var i=boxIx-1; i>=0; i--) {
box[i].style.backgroundColor ="#666";
box[i].style.top = "0px";
box[i].style.zIndex = z;
z = z - 1;
} // End for
z = 8;
for (var i=boxIx+1; i<box.length; i++) {
box[i].style.backgroundColor = "#666";
box[i].style.top = "0px";
box[i].style.zIndex = z;
z = z - 1;
} // End for
} // End browseLeft
As thirtydot pointed out, you have two instances of "**" in your sample code that I've removed in the assumption that this is a markdown glitch when editing.
Your example shows only the JavaScript code. The HTML markup and CSS styling you're using would be most helpful. I've created a fiddle for discussion and to resolve this for you here: http://jsfiddle.net/bhofmann/zkZMD/
A few things I noticed that might be helpful:
You're using a magic number 8 in a few places. Can we assume this is the number of boxes? I would store that in a variable for use in the functions.
You used a lot of direct styling. Your code might be cleaner if you used CSS classes to alter the appearance of the boxes.
Unless you're altering the default styling of DIV, you won't see much change by simply setting the left offset.
PS. I took the liberty of invoking the init function on page load because I saw nothing else to invoke it. I don't know what would invoke browseLeft and browseRight but I'll leave that to you.