How to zip (compress) a JS array - javascript

How would I compress an array?
I am trying to compress an array. I have tried using the lz-string library and converting to/from strings, but I get null/0/[] on decompress.
This is what I'm doing:
var array = [];
for (var i = 0; i < 1024; i++) {
array[array.length] = i % 255;
}
var string = String.fromCharCode.apply(null, array);
var compressed = LZString.compress(string);
var decompressed = LZString.decompress(compressed);
var dearray = [];
for (var i = 0; i < decompressed.length; i++) {
dearray[i] = decompressed.charCodeAt(i);
}
http://jsfiddle.net/ZV5Za/18/

The problem seems to be in the way you're forming the array into a string, and back.
Why not use String.prototype.split() / Array.prototype.join() (Fiddle):
var string = array.join('|');
var dearray = decompressed.split('|');
Or maybe even better: JSON.stringify() / JSON.parse() (Fiddle)
(This actually preserves data types):
var string = JSON.stringify(array);
var dearray = JSON.parse(decompressed);
I don't know how you'd fix the "string -> array" step you are using, though.

Turns out it does work, I just had a typo.
http://jsfiddle.net/ZV5Za/20/
var array = [];
for (var i = 0; i < 1024; i++) {
array[array.length] = i % 255;
}
var string = String.fromCharCode.apply(null, array);
var compressed = LZString.compress(string);
var decompressed = LZString.decompress(compressed);
var dearray = [];
for (var i = 0; i < decompressed.length; i++) {
dearray[i] = decompressed.charCodeAt(i);
}
console.log(array.length, array);
console.log(string.length, string);
console.log(compressed.length, compressed);
console.log(decompressed.length, decompressed);
console.log(dearray.length, dearray);

Related

Alternately Join 2 strings - Javascript

I have 2 strings and I need to construct the below result (could be JSON):
indexLine: "id,first,last,email\n"
dataLine: "555,John,Doe,jd#gmail.com"
Result: "id:555,first:john,....;
What would be the fastest way of joining alternately those 2 strings?
I wrote this - but it seems too straight forward:
function convertToObject(indexLine, dataLine) {
var obj = {};
var result = "";
for (var j = 0; j < dataLine.length; j++) {
obj[indexLine[j]] = dataLine[j]; /// add property to object
}
return JSON.stringify(obj); //-> String format;
}
Thanks.
var indexLine = "id,first,last,email";
var dataLine = "555,John,Doe,jd#gmail.com";
var indexes = indexLine.split(',');
var data = dataLine.split(',');
var result = [];
indexes.forEach(function (index, i) {
result.push(index + ':' + data[i]);
});
console.log(result.join(',')); // Outputs: id:555,first:John,last:Doe,email:jd#gmail.com
If you might have more than one instance of your object to create, you could use this code.
var newarray = [],
thing;
for(var y = 0; y < rows.length; y++){
thing = {};
for(var i = 0; i < columns.length; i++){
thing[columns[i]] = rows[y][i];
}
newarray.push(thing)
}
source

What is the correct way to use an Array in Javascript?

I'm new to javascript. So this question might not be good.
var arrQue = new Array(10);
for (var i = 0; i < 10; i++) {
arrQue[i] = new Array(6);
}
This code works perfectly but I wanted to know without giving the array size, how can I make something like this (the following code doesn't work):
var arrQue = new Array();//don't know the size
for (var i = 0; i < arrQue.length; i++) {
arrQue[i] = new Array();//don't know the size
}
And also the code contains two times creating new array. Is there easier or best way to do that creating multiple array?
And later I've to access like this:
arrQue[0][6] = "test";
arrQue[23][3] = "some test";
I found this method but think wrong somehow?
Object.size = function(obj) {
var size = 0, key;
for (key in obj) {
if (obj.hasOwnProperty(key)) size++;
}
return size;
};
var arrQue = [];
var size = Object.size(arrQue);
for (var i = 0; i < size; i++) {
arrQue[i] = [];
var nextSize = Object.size(arrQue[i]);
}
var arrQue = [];
for (var i = 0; i < length of your inputs; i++) {
arrQue.push(input);
}
Take a look here
Check out the Array Object Methods there.. that's all the stuff you need.
You can have arrays,arrays of objects... etc..depending upon your requirement.
var arrQue = [];
for (var i = 0; i < 10; i++) {
arrQue.push(input);
}
you might be looking for the push method:
var arr = [];
arr.push(your value);

How to build an array from a string in javascript?

I am trying to grab some values out of a sting that looks like this:
W1:0.687268668116, URML:0.126432054521, MH:0.125022031608, W2:0.017801539275, S3:0.00869514129605, PC1:0.00616885024382, S5L:0.0058163445156, RM1L:0.00540508783268, C2L:0.00534633687797, S4L:0.00475882733094, S2L:0.00346630632748
I want to make an array of all the keys and another array of all the values i.e. [W1, URML, MH…] and [0.687268668116, 0.126432054521...]
I have this snippet that does the trick, but only for the first value:
var foo = str.substring(str.indexOf(":") + 1);
Use split().
Demo here: http://jsfiddle.net/y9JNU/
var keys = [];
var values = [];
str.split(', ').forEach(function(pair) {
pair = pair.split(':');
keys.push(pair[0]);
values.push(pair[1]);
});
Without forEach() (IE < 9):
var keys = [];
var values = [];
var pairs = str.split(', ');
for (var i = 0, n = pairs.length; i < n; i++) {
var pair = pairs[i].split(':');
keys.push(pair[0]);
values.push(pair[1]);
};
This will give you the keys and values arrays
var keys = str.match(/\w+(?=:)/g),
values = str.match(/[\d.]+(?=,|$)/g);
RegExp visuals
/\w+(?=:)/g
/[\d.]+(?=,|$)/g
And another solution without using regexp
var pairs = str.split(" "),
keys = pairs.map(function(e) { return e.split(":")[0]; }),
values = pairs.map(function(e) { return e.split(":")[1]; });
JSFiddle
var str = "W1:0.687268668116, URML:0.126432054521, MH:0.125022031608, W2:0.017801539275, S3:0.00869514129605, PC1:0.00616885024382, S5L:0.0058163445156, RM1L:0.00540508783268, C2L:0.00534633687797, S4L:0.00475882733094, S2L:0.00346630632748";
var all = str.split(","),
arrayOne = [],
arrayTwo = [];
for (var i = 0; i < all.length; i++) {
arrayOne.push(all[i].split(':')[0]);
arrayTwo.push(all[i].split(':')[1]);
}
parse the string to an array
var str = "W1:0.687268668116, URML:0.126432054521, MH:0.125022031608, W2:0.017801539275";
var tokens = str.split(",");
var values = tokens.map(function (d) {
var i = d.indexOf(":");
return +d.substr(i + 1);
});
var keys = tokens.map(function (d) {
var i = d.indexOf(":");
return d.substr(0, i);
});
console.log(values);
console.log(keys);
http://jsfiddle.net/mjTWX/1/ here is the demo

how can I parse json with multiple lines

I have the following JSON:
[{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557704","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557705","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557706","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557707","mobile":"400089151"}]
I need to extract all "phoneNumber" using a js function.
I'm testing from using html and my function is not so good:
function getNumbers(strJSON)
{
strJSON = "[{\"errorMessage\":\"success\",\"mobile\":\"400089151\",\"phoneNumber\":\"400557704\",\"returnCode\":\"0\"},{\"errorMessage\":\"success\",\"mobile\":\"400089151\",\"phoneNumber\":\"400557705\",\"returnCode\":\"0\"},{\"errorMessage\":\"success\",\"mobile\":\"400089151\",\"phoneNumber\":\"400557706\",\"returnCode\":\"0\"}]";
var len = strJSON.length;
var begin_index = strJSON.indexOf("returnCode") - 2;
var last_index = len - 1;
var string_toSplit = strJSON.substring(begin_index, last_index);
var string_splitted = string_toSplit.split("{");
var out="";
alert(strJSON);
alert("string_splitted");
alert(string_splitted);
for ( var i = 0; i < string_splitted.length; i++)
{
if (string_splitted[i].charAt(string_splitted[i].length - 1) === ",")
{
string_splitted[i] = string_splitted[i].slice(0, -1);
}
var json = "{" + string_splitted[i];
var obj = JSON.parse(json);
if (i == string_splitted.length)
{
out = out + obj.phoneNumber;
}
else
{
out = out + obj.phoneNumber + ",";
}
}
return out;
}
For modern browsers you can use the .map() method
var j = [{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557704","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557705","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557706","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557707","mobile":"400089151"}];
var phones = j.map(function(item){return item.phoneNumber});
Update
After seeing your code (do not try to manually split/parse the json string.. use the JSON.parse method) you should use
function getNumbers(strJSON)
{
var myJson = JSON.parse( strJSON );
return myJson.map(function( item ){ return item.phoneNumber}).join(',');
}
Update: An even better way:
function getNumbers(strJSON)
{
var obj = JSON.parse(strJSON);
return obj.map(x => x.phoneNumber).join(", ")
}
Original Post:
A straight forward method is to just iterate over every object in the array and take the values out individually.
var info = [{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557704","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557705","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557706","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557707","mobile":"400089151"}];
var phoneNumbers = [];
for (var i = 0; i < info.length; i++)
{
phoneNumbers.push(info[i].phoneNumber);
}
console.log(phoneNumbers);
http://jsfiddle.net/hX69r/
UPDATE:
http://jsfiddle.net/hX69r/1/
var info = [{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557704","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557705","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557706","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557707","mobile":"400089151"}];
var infoString = JSON.stringify(info); //this just turns the object array 'info' into a string
var numbers = getNumbers(infoString);
console.log(numbers);
function getNumbers(strJSON)
{
var obj = JSON.parse(strJSON);
var phoneNumbers = [];
for (var i = 0; i < obj.length; i++)
{
phoneNumbers.push(obj[i].phoneNumber);
}
return phoneNumbers.join(", ");
}
Additional Update:
var info = [{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557704","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557705","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557706","mobile":"400089151"},
{"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557707","mobile":"400089151"}];
var infoSingle = {"returnCode":"0","errorMessage":"success","Code":{},"phoneNumber":"400557704","mobile":"400089151"};
console.log(info.length); // prints 4; so you know it has the []
console.log(infoSingle.length); // prints undefined; so you know it doesn't have []
Do not try to re-invent the wheel.
There are many ways to parse JSON already:
Use JSON.parse.
Use jQuery.parseJSON

How to create an array like this in JavaScript?

I want to create an array like this:
s1 = [[[2011-12-02, 3],[2011-12-05,3],[5,13.1],[2011-12-07,2]]];
How to create it using a for loop? I have another array that contains the values as
2011-12-02,3,2011-12-05,3,2011-12-07,2
One of possible solutions:
var input = ['2011-12-02',3,'2011-12-05',3,'2011-12-07',2]
//or: var input = '2011-12-02,3,2011-12-05,3,2011-12-07,2'.split(",");
var output = [];
for(i = 0; i < input.length; i += 2) {
output.push([t[i], t[i + 1]])
}
If your values always come in pairs:
var str = '2011-12-02,3,2011-12-05,3,2011-12-07,2',//if you start with a string then you can split it into an array by the commas
arr = str.split(','),
len = arr.length,
out = [];
for (var i = 0; i < len; i+=2) {
out.push([[arr[i]], arr[(i + 1)]]);
}
The out variable is an array in the format you requested.
Here is a jsfiddle: http://jsfiddle.net/Hj6Eh/
var s1 = [];
for (x = 0, y = something.length; x < y; x++) {
var arr = [];
arr[0] = something[x].date;
arr[1] = something[x].otherVal;
s1.push(arr);
}
I've guessed here that the date and the other numerical value are properties of some other object, but that needn't be the case...
I think you want to create an array which holds a set of arrays.
var myArray = [];
for(var i=0; i<100;i++){
myArray.push([2011-12-02, 3]); // The values inside push should be dynamic as per your requirement
}

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