This question is a bit hard to explain so please tell me if this is not clear.
Firstly, i have a .map() function to handle some data, and since it is a for loop, it might generate a big amount of data.
And when i console.log() it , I realize that the Array has been slice in to [0-99],[100-200] like the image below.
And when i pass the array thing via node.js to the backend it turns out like below:
it passes all the number to backend as well and cause exception, how may i get rid of these numbers? It's working fine if the array didn't exceed 100
it not suppose to have something like "0":["1","2"]
[]3
Ok let's make everything clear. When the array "NOT" exceeding 100 it would pass normal array to the backend like below:
The problem is when it exceed 100 it will pass something like below instead and which our backed system cannot read it due to the array has some wield contains.
I am using .slice() to limit the max lenght of the array, so users need to upload data 100 per time but i want to see if there's anyway to fix it, may i could use .slice(), turn huge array into tiny pieces and .join() it back together?
UPDATE:
var array = $(".AdvKeyowrdAND").map(function() {
return [$(this).html().replace(/\+/g,',').split(",")];
}).get();
The above is the actualy Javascript code which handle all the elements
Related
I want to perform MapReduce job on data in Riak DB using javascript. But stuck in very begining, i couldnot understand how it is returning value.
client = riak.RiakClient()
query = client.add('user')
query.map("""
function(v){
var i=0;
i++;
return [i];
}
""")
for result in query.run():
print "%s" % (result);
For simplicity i have checked the above example.
Here query is bucket and user contain five sets of data in RiakDB.
i think map() returns single value but it returns array with 5 value, i think equivalent to five set of data in RiakDB.
1
1
1
1
1
And here, why I can return only array? it treats each dataset independently, and returns for each. so i think i have five 1's. Due to this reason when i process fetched data inside map(), returns gives unexpected result for me.
so please give me some suggestion. i think it is basic thing but i couldnot get it. i highly appreciate your help.
When you run a MapReduce job, the map phase code is sent out to the vnodes where the data is stored and executed for each value in the data. The resulting arrays are collected and passed to a single reduce phase, which also returns an array. If there are sufficiently many results, the reduce phase may be run multiple times, with the previous reduce result and a batch of map results as input.
The fact that you are getting 5 results implies that 5 keys were seen in your bucket. There is no global state shared between instances of the map phase function, so each will have an independent i, which is why each result is 1.
You might try returning [v.key] so that you have something unique for each one, or if the values are expected to be small, you could return [JSON.stringify(v)] so you can see the entire structure that is passed to the map.
You should note that according to the docs site javascript Map Reduce has been officially deprecated, so you may want to use Erlang functions for new development.
I've got a mock up indexedDB holds items like:
{
id:1002,
name:"Frank",
company: "dg",
age:30
}
And I've created the index ['name','age','company'] , just want to get the result I need like websql do.
getMultipleDataByRange function defined to get items, I set ['0',24,'ef'] as lowerBound and ['z',24,'ef'] as upperBound, I thought it should show me the result match the items who's 24 years old plus whose company is "ef". But the result shows that all the items meet the range I set. How can I set the range to get the correct result.
Code can also be checked by JSBIN link I generated:
http://jsbin.com/sinuxa/edit?js,console
It'll work if you change the order of your index so that the part that varies (name) is at the end. If you want to know why, see In IndexedDB, is there a way to make a sorted compound query? for an explanation of how compound indexes work in IndexedDB.
I have a website that will give you a random fact from Wikipedia when you click a big red button. I have heard from a few people that they are getting certain facts repeatedly, even though there are over 200.
The big red button has onclick="giveafact()" which triggers this function:
function giveafact(){ //instead of relisting all array items here, add all the other arrays to this one
var factsList= foodFactsList.concat(musicFactsList,historyFactsList,popFactsList,sportsFactsList,technologyFactsList,televisionFactsList,miscFactsList);
randomFact = Math.floor(Math.random()*factsList.length);
document.getElementById("total").innerHTML=factsList.length;
document.getElementById("fact").innerHTML=factsList[randomFact];
updateShareLinks();
return false;
}
Basically, I have 8 different arrays of facts as you can see in var factsList above. This is so the user can filter by fact. By default, there is no filter so all lists are concatenated.
If it helps, the full .js file is here: http://thewikifix.com/scripts/script.js. These random "give a fact" functions start at about line 442, with the arrays above them. (Pardon the messy code, I know I mix jQuery and Javascript a lot.)
The site is http://thewikifix.com, if it helps anyone to look at all the code.
I'm just trying to see if there's a way to better randomize the facts than I currently have, maybe by adding a function that won't allow a fact to show up twice in a row, or something similar.
Any suggestions would be great!
Edit - Additional thoughts: Thanks for the answers so far. Is there a way to remove an item from an array once it has been picked via the Math.random function so it just wouldn't show up again at all (unless the page was refreshed)? If so, once all items were removed from the array is there a way to reset the array to its original state without the user having to refresh? Thanks.
"Random" and "varied" are, to some extent, conflicting. With 200 facts, and one selected randomly each time, it becomes more likely than not that you'll see a repeat after getting only a couple dozen or so (this is known as the "Birthday Problem").
A simple approach is to store a seed and an index on the client. The seed is set once, and the index is incremented after each fact access. To get a "random" fact, seed a PRNG with the seed, use the PRNG to shuffle the list of facts, then get the fact at the given index in the shuffled list. When you run out, pick a new seed and reset the index.
Here's what I would do:
n = 0 - Find a random fact
add that fact to a new array (arr)
display fact
n + 1 - Find a random fact
check arr using lodash for that facts existence
display or find a new fact, based on result of above
--OR--
you could take the arr and use lodash's _.shuffle() to mix them up and display them in order.
https://lodash.com/docs
I love using lodash for collection and array operations.
Trying to plan out a function and I wanted to get some input. I am trying to find an efficient way to:
Double the frequency of numbers in an array
Randomize the location of the values in the array.
For example: Lets say I have an array. [0,1,2,3]
first I want to duplicate each number once in a new array. So now we would have something like this.
[0,0,1,1,2,2,3,3].
Lastly, I want to randomize these values so: [0,4,2,3,0,2,3,4]
Eventually, the algorithm I write will need to handle an initial array of 18 digits (so the final, randomized array will be of size 36)
My initial thoughts are to just have a simple while loop that:
Randomly selects a spot in the new array
Checks to see if it is full
-If it is full, then it will select a new spot and check again.
If it is not full, then it will place the value in the new array, and go to the next value.
I am leaving out some details, etc. but I want this algorithm to be fairly quick so that the user doesn't notice anything.
My concern is that when there is only one digit left to be placed, the algorithm will take forever to place it because there will be a 1/36 chance that it will select the empty space.
In general terms, how can I make a smarter and faster algorithm to accomplish what I want to do?
Many thanks!
first I want to duplicate each number once in a new array. So now we would have something like this. [0,0,1,1,2,2,3,3].
That would be rather complicated to accomplish. Since the positions are not relevant anyway, just build [0,1,2,3,0,1,2,3] by
var newArray = arr.concat(arr);
Lastly, I want to randomize these values so: [0,4,2,3,0,2,3,4]
Just use one of the recognized shuffle algorithms - see How to randomize (shuffle) a JavaScript array?. There are rather simple ones that run in linear time and do not suffer from the problem you described, because they don't need to randomly try.
Here is an alternative to the known methods with two arrays, I came up with. It gives relatively good randomization.
var array1=[]
var array=[0,1,2,3,0,1,2,3]
a=array.length;
b=a;
c=b;
function rand(){for (i=0;i<c;i++){
n=Math.floor(Math.random()*b);
array1[i]=array[n]; array.splice(n,1);b--;}
for (i1=0;i1<c;i1++){array[i1]=array1[i1]}
It is my understanding that -- from a performance perspective -- direct assignment is more desirable than .push() when populating an array.
My code is currently as follows:
for each (var e in Collection) {
do {
DB_Query().forEach(function(e){data.push([e.title,e.id])});
} while (pageToken);
}
DB_Query() method runs a Google Drive query and returns a list.
My issue arises because DB_Query() can return a list of variable length. As such, if I construct data = new Array(100), direct assignment has the potential to go out of bounds.
Is there a method by which I could try and catch an Out of Bounds exception to have values directly assigned for the 100 pre-allocated indices, but use .push() for any overflow? The expectation here is that an OOB exception will not occur often.
Also, I'm not sure if it matters, but I am clearing the array after a counter variable is >=100 using the following method:
while(data.length > 0) {data.pop()}
In Javascript, if you set a value at an index bigger than the array length, it'll automatically "stretch" the array. So there's no need to bother with this. If you can make a good guess about your array size, go for it.
About your clearing loop: that's correct, and it seems that pop is indeed the fastest way.
My original suggestion was to set the array length back to zero: data.length = 0;
Now a tip that I think really makes a performance difference here: you're worrying with the wrong part!
In Apps Script, what takes long is not resizing arrays dynamically, or working your data, that's fast. The issue is always with the "API calls". That is, using UrlFetch or Spreadsheet.Range.getValue and so on.
You should take care to make the minimum amount of API calls possible and in your case (I'm guessing now, since I haven't seen your whole code) you seem to be doing it wrong. If DB_Query is costly (in API calls terms) you should not have it nested under two loops. The best solution usually involves figuring out everything you'll need before-hand (do as many loops you need, if it doesn't call anywhere), then pass all parameters to do a bulk operation and gather it all at once (in one API call), even if it involves getting more data than you needed. Then, with the whole data at hand, loop through and transform it as required (that's the fast part).