Im still needing help with this, and have edited the jsfiddle post to show my problem. http://jsfiddle.net/7ztEf/6/
I want to return number to associated index value [0] =0 [1]=1 as you can see the index string returns all numbers. Thanks again Paul
I have a number generator script that returns values to DIV ID's. I need to hook into this somehow, to enable replacing color based upon the number value i.e. > 1 && <= 20 = red etc.
function myNumbers(numbers, type) {
for (var x in numbers) {
document.getElementById(type + x).innerHTML = numbers[x];
}
}
This script fills each of the DIVs named num0 ... num3 with a random number.
I have managed to query the first value of numbers[x] but need to set an index order to loop through the rest, or something.
Use Array.forEach.
numbers.forEach(function (number, index) {...})
Don't use for..in for arrays. They're meant to be used on objects so using for..in on arrays will return such things as the length element.
Either use forEach as ethagnawl mentioned or use the traditional for loop:
for (var x=0; x < numbers.length; x++) {
document.getElementById(type + x).innerHTML = numbers[x];
}
Related
ı couldn't pop() every array list. at the end remain two array elements
function ürünSil(){
let diller = [ "Türkçe", "İngilizce", "Almanca", "Fransızca", "Japonca"]
for(let i in diller){
let sonİcerik = diller.pop()
document.write(diller + "<br />")
}
}
you can empty your array like this also:
let diller = [ "Türkçe", "İngilizce", "Almanca", "Fransızca", "Japonca"];
while(diller.length > 0) {
diller.pop();
}
console.log(diller)
The length of the array changes each time on pop() so when there are 3 items removed from the array , the present index for i on your code will be 2 and hence the actual length is also 2, so the for() loops does not trigger further.
The solution could be to preserve the initial length value and use that value in the loop:
function ürünSil(){
let diller = [ "Türkçe", "İngilizce", "Almanca", "Fransızca", "Japonca"]
const length = diller.length;
for(let i = 0; i<length; i++){
let sonİcerik = diller.pop()
console.log(sonİcerik);
}
}
ürünSil()
use while loop instead of for.
while (diller.length != 0) {
diller.pop();
document.write(diller + '<br />');
}
This happens because pop reduces the length of the array, which impacts the times the loop will iterate. Instead just have the while condition check whether the array still has elements, without any i.
Unrelated, but
don't use document.write for this. Use console.log, or if you want to add data to the HTML document, then use other DOM methods.
have the good habit of ending your statements with semicolon. You don't want to fall for the sometimes tricky effects of automatic semicolon insertion.
let diller = [ "Türkçe", "İngilizce", "Almanca", "Fransızca", "Japonca"];
while (diller.length) {
let sonİcerik = diller.pop();
console.log(sonİcerik);
}
I'm working on a calculation form that generates a multi-dimensional array with two values [selection], something like:
[[10,0.5], [18,0.75]]
The second array [lookup-table] contains a range of values:
["10","0.5","0.1"], ["12","0.5","1.1"], ["14","0.5","3.1"], ["16","0.5","5.1"],["18","0.5","7.1"], ["20","0.5","9.6"], ["22","0.5","11.6"]... ["18","0.75","9.1"]
I'm trying to match the index [0], [1] values in the [selection] array with the same index values in the [lookup-table] array.
["10","0.5","0.1"]... ["18","0.75","9.1"]
Once this is done, I'd like to retrieve the value for the index [x][2] value in the [lookup-table]:
["10","0.5","0.1"]... ["18","0.75", "9.1"]
I did find a very helpful and similar question here: JavaScript - Compare two multidimensional arrays
And in the console, it seems to correctly identify matches in the array index.
I'm using more or less a similar function:
function find(haystack, needles) {
var lookupValue = [];
//Iterate through all elements in first array
for(var x = 0; x < haystack.length; x++){
//Iterate through all elements in second array
for(var y = 0; y < needles.length; y++){
/*This causes us to compare all elements
in first array to each element in second array
Since haystack[x] stays fixed while needles[y] iterates through second array.
We compare the first two indexes of each array in conditional
*/
if(haystack[x][0] == needles[y][0] && haystack[x][1] == needles[y][1]){
console.log("match found");
console.log("Array 1 element with index " + x + " matches Array 2 element with index " + y);
//Retrieve the price for the high and low lookup values and store in array
lookupValue = haystack[x][2];
}
}
}
return lookupValue;
}
var totalResult = find(lookupTable, flushGrowthArray ).toString();
However when I try to retrieve the haystack[x][2] indexed value from the matches in the [lookup-table], for some reason I'm only returning a single value.
I think that it's probably a very simple mistake; what am I doing wrong? I appreciate any new insights.
lookupValue = haystack[x][2];
should be:
lookupValue.push(haystack[x][2]);
so you add the match to the array.
I want to access values of below elments
opener.document.EditView.flight_no1_c.value
opener.document.EditView.flight_no2_c.value
opener.document.EditView.flight_no3_c.value
opener.document.EditView.flight_no4_c.value
Here only numbers are changing ranging from 1 to 4.
How can I make this into loop.
You can use for loop and call properly using [] insteand on ., see below code
for(var i = 1; i <= 4; i++ ){
opener.document.EditView["flight_no"+i+"_c"].value
}
what about
for(var key in opener.document.EditView){
if(key.match(/^flight_no\d+_c/)){
console.log(key.value);
}
}
I'm new to javascript and have been trying to teach myself the basics. I do have some experience with C++.
I came across this example in the source I'm using for studying and the for loop looks strange to me:
<html>
<head>
<script type="text/javascript">
<!--
function ReadCookie()
{
var allcookies = document.cookie;
alert("All Cookies : " + allcookies );
// Get all the cookies pairs in an array
cookiearray = allcookies.split(';');
// Now take key value pair out of this array
for(var i=0; i<cookiearray.length; i++){
name = cookiearray[i].split('=')[0];
value = cookiearray[i].split('=')[1];
alert("Key is : " + name + " and Value is : " + value);
}
}
//-->
</script>
</head>
<body>
<form name="myform" action="">
<input type="button" value="Get Cookie" onclick="ReadCookie()"/>
</form>
</body>
</html>
Would someone mind explaining why there is a [0] and [1] near the end of these statements?
name = cookiearray[i].split('=')[0];
value = cookiearray[i].split('=')[1];
A clearer way to write this statement is this:
var parts = cookiearray[i].split('='),
name = parts[0],
value = parts[1];
That doesn't have anything to do with the for-loop itself. Split returns an array of tokens; the string is split up at the given delimiter. You're simply accessing the first and second tokens in this array.
String.split creates an array using the assigned delimiter (in this case '='). The [0] and [1] are selecting the first and second elements of the array respectively (Javascript array element indexes start at zero).
Those are used to access the items in the arrays that you create.
It's more clear what they do, and also better for performance, if you put the array in a variable and access that. That way you don't have to create two identical arrays:
var cookie = cookiearray[i].split('=');
var name = cookie[0];
var value = cookie[1];
The code is splitting each cookie pair key=value into key ([0]) and value ([1]).
A for loop is an iterator. You can sort of think of it like a counter, or stepping progression. If you want to do something x number of times, then a for loop is your best friend. The issue, when you are first learning, is figuring out how to use them effectively.
I'll give you a relevant and nonrelevant (simplified) example:
Nonrelevant:
// Increase the value of x and print the new value to the console 20 times.
var x = 6;
for(var i = 0; i < 20; i++) {
x++;
console.log("Value of x: " + x);
}
If you take a close look it's really rather logical. You define an iteration variable i, tell it when to stop (i < 20...so stop if i = 20), how to progress with each iteration (i++ or i + 1).
So the code will enter the loop when i = 0...it will add 1 to the value of x (x++), resulting in x = 7. It does the same for each iteration, so when i = 1, x (7) + 1 = 8, so on and so forth until i = 20, then the code breaks out of the loop and continues on it's merry little way. When it breaks we have just added 1 to x 20 times. Since x used to equal 6, it now equals 26.
Relevant:
// Given array of length 10, print each element to the console
for (var i = 0; i < cookiearray.length; i++){
console.log(cookiearray[i]);
}
So here the for loop is the same, it simply iterates until i equals the length (number of elements, in this case) of the array (so 10 times). When i = 0, our code prints the element of the array at cookiearray[0]...when i = 1 it prints cookiearray[1]...so on and so forth for the entirety of the array.
What may confuse you in the example is the split function. Split returns an array. So this line:
name = cookiearray[i].split('=')[0];
...actually means assign the first element of the new array created from splitting the cookiearray's element at position i.
Let's assume that cookiearray[0] = "Hello=World". When i = 0, our code splits the string "Hello=World" into a new array where the element at the 0 position is "Hello", it then assigns this to the local variable name. So name = "Hello".
Situation
I'm currently writing a javascript widget that displays a random quote into a html element. the quotes are stored in a javascript array as well as how many times they've been displayed into the html element. A quote to be displayed cannot be the same quote as was previously displayed. Furthermore the chance for a quote to be selected is based on it's previous occurences in the html element. ( less occurrences should result in a higher chance compared to the other quotes to be selected for display.
Current solution
I've currently made it work ( with my severely lacking javascript knowledge ) by using a lot of looping through various arrays. while this currently works ( !! ) I find this solution rather expensive for what I want to achieve.
What I'm looking for
Alternative methods of removing an array element from an array, currently looping through the entire array to find the element I want removed and copy all other elements into a new array
Alternative method of calculating and selecting a element from an array based on it's occurence
Anything else you notice I should / could do different while still enforcing the stated business rules under Situation
The Code
var quoteElement = $("div#Quotes > q"),
quotes = [[" AAAAAAAAAAAA ", 1],
[" BBBBBBBBBBBB ", 1],
[" CCCCCCCCCCCC ", 1],
[" DDDDDDDDDDDD ", 1]],
fadeTimer = 600,
displayNewQuote = function () {
var currentQuote = quoteElement.text();
var eligibleQuotes = new Array();
var exclusionFound = false;
for (var i = 0; i < quotes.length; i++) {
var iteratedQuote = quotes[i];
if (exclusionFound === false) {
if (currentQuote == iteratedQuote[0].toString())
exclusionFound = true;
else
eligibleQuotes.push(iteratedQuote);
} else
eligibleQuotes.push(iteratedQuote);
}
eligibleQuotes.sort( function (current, next) {
return current[1] - next[1];
} );
var calculatePoint = eligibleQuotes[0][1];
var occurenceRelation = new Array();
var relationSum = 0;
for (var i = 0; i < eligibleQuotes.length; i++) {
if (i == 0)
occurenceRelation[i] = 1 / ((calculatePoint / calculatePoint) + (calculatePoint / eligibleQuotes[i+1][1]));
else
occurenceRelation[i] = occurenceRelation[0] * (calculatePoint / eligibleQuotes[i][1]);
relationSum = relationSum + (occurenceRelation[i] * 100);
}
var generatedNumber = Math.floor(relationSum * Math.random());
var newQuote;
for (var i = 0; i < occurenceRelation.length; i++) {
if (occurenceRelation[i] <= generatedNumber) {
newQuote = eligibleQuotes[i][0].toString();
i = occurenceRelation.length;
}
}
for (var i = 0; i < quotes.length; i++) {
var iteratedQuote = quotes[i][0].toString();
if (iteratedQuote == newQuote) {
quotes[i][1]++;
i = quotes.length;
}
}
quoteElement.stop(true, true)
.fadeOut(fadeTimer);
setTimeout( function () {
quoteElement.html(newQuote)
.fadeIn(fadeTimer);
}, fadeTimer);
}
if (quotes.length > 1)
setInterval(displayNewQuote, 10000);
Alternatives considered
Always chose the array element with the lowest occurence.
Decided against this as this would / could possibly reveal a too obvious pattern in the animation
combine several for loops to reduce the workload
Decided against this as this would make the code to esoteric, I'd probably wouldn't understand the code anymore next week
jsFiddle reference
http://jsfiddle.net/P5rk3/
Update
Rewrote my function with the techniques mentioned, while I fear that these techniques still loop through the entire array to find it's requirements, at least my code looks cleaner : )
References used after reading the answers here:
http://www.tutorialspoint.com/javascript/array_map.htm
http://www.tutorialspoint.com/javascript/array_filter.htm
http://api.jquery.com/jQuery.each/
I suggest array functions that are mostly supported (and easily added if not):
[].splice(index, howManyToDelete); // you can alternatively add extra parameters to slot into the place of deletion
[].indexOf(elementToSearchFor);
[].filter(function(){});
Other useful functions include forEach and map.
I agree that combining all the work into one giant loop is ugly (and not always possible), and you gain little by doing it, so readability is definitely the winner. Although you shouldn't need too many loops with these array functions.
The answer that you want:
Create an integer array that stores the number of uses of every quote. Also, a global variable Tot with the total number of quotes already used (i.e., the sum of that integer array). Find also Mean, as Tot / number of quotes.
Chose a random number between 0 and Tot - 1.
For each quote, add Mean * 2 - the number of uses(*1). When you get that that value has exceeded the random number generated, select that quote.
In case that quote is the one currently displayed, either select the next or the previous quote or just repeat the process.
The real answer:
Use a random quote, at the very maximum repeat if the quote is duplicated. The data usages are going to be lost when the user reloads/leaves the page. And, no matter how cleverly have you chosen them, most users do not care.
(*1) Check for limits, i.e. that the first or last quota will be eligible with this formula.
Alternative methods of removing an array element from an array
With ES5's Array.filter() method:
Array.prototype.without = function(v) {
return this.filter(function(x) {
return v !== x;
});
};
given an array a, a.without(v) will return a copy of a without the element v in it.
less occurrences should result in a higher chance compared to the other quotes to be selected for display
You shouldn't mess with chance - as my mathematician other-half says, "chance doesn't have a memory".
What you're suggesting is akin to the idea that numbers in the lottery that haven't come up yet must be "overdue" and therefore more likely to appear. It simply isn't true.
You can write functions that explicitly define what you're trying to do with the loop.
Your first loop is a filter.
Your second loop is a map + some side effect.
I don't know about the other loops, they're weird :P
A filter is something like:
function filter(array, condition) {
var i = 0, new_array = [];
for (; i < array.length; i += 1) {
if (condition(array[i], i)) {
new_array.push(array[i]);
}
}
return new_array;
}
var numbers = [1,2,3,4,5,6,7,8,9];
var even_numbers = filter(numbers, function (number, index) {
return number % 2 === 0;
});
alert(even_numbers); // [2,4,6,8]
You can't avoid the loop, but you can add more semantics to the code by making a function that explains what you're doing.
If, for some reason, you are not comfortable with splice or filter methods, there is a nice (outdated, but still working) method by John Resig: http://ejohn.org/blog/javascript-array-remove/