I have a string that contains coordinates and some whitesace:
E.G. "SM10,10 50,50 20,10\nFM10,20 30,40"
I'd like to extract the list of coordinates:
["10,10", "50,50", "20,10", "10,20", "30,40"]
And then perform some transform (let's say scale by 5) and produce a resultant string:
"SM50,50 250,250 100,50\nFM50,100 140,200"
What's the most performant way to perform this transformation in JavaScript?
Update:
This should be exactly what you needed. It finds and makes the changes to the coordinates in the string and reassembles the string in the format that it started. Let me know if you think its missing something.
function adjust(input) {
var final = "";
var lastIndex;
var temp = [];
var regex;
var coords = input.match(/\d+,\d+/g);
if (coords) {
for (i = 0; i < coords.length; i++) {
temp = coords[i].split(",");
temp[0] *= 5;
temp[1] *= 5;
regex = new RegExp("([^0-9])?" + coords[i] + "([^0-9])?","g");
regex.exec(input);
lastIndex = parseInt(regex.lastIndex);
final += input.slice(0, lastIndex).replace(regex, "$1" + temp.join(",") + "$2");
input = input.slice(lastIndex, input.length);
temp.length = 0;
}
}
return final + input;
}
Previous answer:
Here, fast and effective:
var coords = "SM10,10 50,50 20,10\nFM10,20 30,40".match(/\d{1,2},\d{1,2}/g);
for (i = 0; i < coords.length; i++) {
var temp = coords[i].split(",");
temp[0] *= 5;
temp[1] *= 5;
coords[i] = temp.join(",");
}
alert (coords.join(","));
Related
var input = `2
6
z2k1o2
6
m2v1p2`
var newInput = input.split("\n")
//console.log(newInput.length)
var input_arr = input.trim().split("\n")
var n = Number(input_arr[0])
//console.log(input_arr)
for (var i = 1; i < input_arr.length; i = i + 2) {
var length = Number(input_arr[i])
var string = input_arr[i + 1].trim()
}
//console.log(string)
var newstring = string
//console.log(newstring)
var alpha = []
var num = []
for (i = 1; i < string.length; i += 2) {
num.push(string[i])
}
var newnum = num.map(Number)
//console.log(newnum)
for (i = 0; i < string.length; i += 2) {
alpha.push(string[i])
}
var newalpha = (alpha)
//console.log(newalpha)
var answer = []
for (i = 0; i < newnum.length; i++) {
for (j = 0; j < newnum[i]; j++) {
answer.push(newalpha[i])
}
}
console.log(answer.join(""))
Here I'm getting only one output can you please explain why And do you like share any other approach for this problem.
This is the input z2k1o2 and the output should be zzkoo
The input will follow this patter of alphabets ans counts..
I'd do this with a regular expression that captures pairs of (character, number) and uses the function-replacement mode of .replace() to generate the replacement string.
> "a2b1c2".replace(/([a-z])([0-9]+)/ig, (_, a, b) => a.repeat(+b))
"aabcc"
>"pos2es2".replace(/([a-z])([0-9]+)/ig, (_, a, b) => a.repeat(+b))
"possess"
Here's where you're running into your error:
for (var i = 1; i < input_arr.length; i = i + 2) {
var length = Number(input_arr[i])
var string = input_arr[i + 1].trim()
}
You're going through the entire input array and saving each of the lengths and strings, but you're overwriting the length and the string each time you read it - only the last length and last string are saved, and so only the last length and last string are processed / printed.
I wrote the following javaScript to try to draw a random path in an svg.
<script>
window.onload = function() {
function randomPath(){
var x = Math.trunc(Math.random());
var y = Math.trunc(Math.random());
var xstep = 0;
var ystep = 0;
var path = '0,0';
for (i = 0; i < 2 ; i++) {
path += ' ';
path += (x).toString();
path += ',';
path += (y).toString();
xstep = Math.random();
ystep = Math.random();
xstep *= 10;
ystep *= 10;
x += Math.trunc(xstep);
y += Math.trunc(ystep);
};
return path;
};
var figure = document.createElementNS('http://www.w3.org/2000/svg','svg');
figure.id = 'brownian-figure';
figure.setAttribute('height', '400pt');
figure.setAttribute('width', '200pt');
var pathArray = [];
for (i = 0; i < 3; i++){
pathArray[i] = document.createElementNS('http://www.w3.org/2000/svg','polyline');
};
for (i = 0; i < 3; i++){
var path = randomPath();
alert(path);
pathArray[i].setAttribute('points', path);
pathArray[i].setAttribute('style', 'fill:none;stroke:rgba(0,0,0,1);stroke-width:1');
figure.appendChild(pathArray[i]);
};
var divfigure = document.createElement('div');
divfigure.id = 'divfigure';
divfigure.style = 'margin:0pt;padding:0pt;border:0pt none;background-color:rgba(240,240,240,1);position:absolute;top:100pt;left:100pt;width:200pt;height:400pt;';
divfigure.appendChild(figure);
document.body.appendChild(divfigure);
};
</script>
Notice there are only 2 steps in the for in the randomPath() function.
The code does run and draws with that small value for the number of steps. There is an alert(path) over there to let me see the path before I try to assign it.
However, with 3 steps or more in the for inside randomPath() the code breaks. The alert(path) still shows the longer path, but the script gives the error
TypeError: pathArray[i] is undefined
pathArray[i].setAttribute('points', path);
If I replace path in the line with the error, by an explicit path (output by randomPath()), say '0,0 0,0 4,8 8,15' it still doesn't work. But if I do it and also remove the call to the randomPath() function it works again.
I am confused. It seems to be that the function randomPath() works well since the alert displays a well-formed string. The svg also works with the same string input explicitly. But the two together don't work for some reason.
What is the problem?
The problem is becoz inside last for loop you have initialise i and incremented it and then you call randomPath() which also contain i and that function increment it to 3 times so when it comes out function you have i value 3
so you get error on pathArray[i].setAttribute('points', path); changed it to k or something in randomPath() and also intialize variable as var identifier if don't want it to be global
for (i = 0; i < 3; i++){
var path = randomPath();
}
window.onload = function() {
function randomPath(){
var x = Math.trunc(Math.random());
var y = Math.trunc(Math.random());
var xstep = 0;
var ystep = 0;
var path = '0,0';
for (k = 0; k < 3 ; k++) {
path += ' ';
path += (x).toString();
path += ',';
path += (y).toString();
xstep = Math.random();
ystep = Math.random();
xstep *= 10;
ystep *= 10;
x += Math.trunc(xstep);
y += Math.trunc(ystep);
}
return path;
}
var figure = document.createElementNS('http://www.w3.org/2000/svg','svg');
figure.id = 'brownian-figure';
figure.setAttribute('height', '400pt');
figure.setAttribute('width', '200pt');
var pathArray = [];
for (j = 0; j < 3; j++){
pathArray[j] = document.createElementNS('http://www.w3.org/2000/svg','polyline');
}
for (i = 0; i < 3; i++){
var path = randomPath();
alert(path);
pathArray[i].setAttribute('points', path);
pathArray[i].setAttribute('style', 'fill:none;stroke:rgba(0,0,0,1);stroke-width:1');
figure.appendChild(pathArray[i]);
}
var divfigure = document.createElement('div');
divfigure.id = 'divfigure';
divfigure.style = 'margin:0pt;padding:0pt;border:0pt none;background-color:rgba(240,240,240,1);position:absolute;top:100pt;left:100pt;width:200pt;height:400pt;';
divfigure.appendChild(figure);
document.body.appendChild(divfigure);
};
I want to remove 3 RANDOM letters from a string.
I can use something like substr() or slice() function but it won't let me take the random letters out.
Here is the demo of what I have right now.
http://jsfiddle.net/euuhyfr4/
Any help would be appreciated!
var str = "hello world";
for(var i = 0; i < 3; i++) {
str = removeRandomLetter(str);
}
alert(str);
function removeRandomLetter(str) {
var pos = Math.floor(Math.random()*str.length);
return str.substring(0, pos)+str.substring(pos+1);
}
If you want to replace 3 random charc with other random chars, you can use 3 times this function:
function substitute(str) {
var pos = Math.floor(Math.random()*str.length);
return str.substring(0, pos) + getRandomLetter() + str.substring(pos+1);
}
function getRandomLetter() {
var letters="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var pos = Math.floor(Math.random()*letters.length);
return letters.charAt(pos);
}
You can split the string to an array, splice random items, and join back to a string:
var arr = str.split('');
for(var i=0; i<3; ++i)
arr.splice(Math.floor(Math.random() * arr.length), 1);
str = arr.join('');
var str = "cat123",
amountLetters = 3,
randomString = "";
for(var i=0; i < amountLetters; i++) {
randomString += str.substr(Math.floor(Math.random()*str.length), 1);
}
alert(randomString);
fiddle:
http://jsfiddle.net/euuhyfr4/7/
This answer states that
It is faster to slice the string twice [...] than using a split followed by a join [...]
Therefore, while Oriol's answer works perfectly fine, I believe a faster implementation would be:
function removeRandom(str, amount)
{
for(var i = 0; i < amount; i++)
{
var max = str.length - 1;
var pos = Math.round(Math.random() * max);
str = str.slice(0, pos) + str.slice(pos + 1);
}
return str;
}
See also this fiddle.
you can shuffle characters in your string then remove first 3 characters
var str = 'congratulations';
String.prototype.removeItems = function (num) {
var a = this.split(""),
n = a.length;
for(var i = n - 1; i > 0; i--) {
var j = Math.floor(Math.random() * (i + 1));
var tmp = a[i];
a[i] = a[j];
a[j] = tmp;
}
return a.join("").substring(num);
}
alert(str.removeItems(3));
You can use split method without any args.
This would return all chars as a array.
Then you can use any randomiser function as described in Generating random whole numbers in JavaScript in a specific range? , then use that position to get the character at that position.
Have a look # my implementation here
var str = "cat123";
var strArray = str.split("");
function getRandomizer(bottom, top) {
return Math.floor( Math.random() * ( 1 + top - bottom ) ) + bottom;
}
alert("Total length " + strArray.length);
var nrand = getRandomizer(1, strArray.length);
alert("Randon number between range 1 - length of string " + nrand);
alert("Character # random position " + strArray[nrand]);
Code # here https://jsfiddle.net/1ryjedq6/
I have been working on a conversion of a C code into javascript. But they just don't return the same data.
I have an idea on how to handle the pointers. In javascript I'll create an array.
Note: This are not the full code, only partials
Origin:
// file.h
unsigned char m_aucState0[256];
unsigned char m_aucState[256];
unsigned char m_ucI;
unsigned char m_ucJ;
unsigned char* m_pucState1;
unsigned char* m_pucState2;
// file.c
unsigned char *pucKeyData
for(i=0; i<256; i++)
{
m_pucState1 = m_aucState0 + i;
m_ucJ += *m_pucState1 + *(pucKeyData+m_ucI);
m_pucState2 = m_aucState0 + m_ucJ;
//Swaping
m_ucTemp = *m_pucState1;
*m_pucState1 = *m_pucState2;
*m_pucState2 = m_ucTemp;
m_ucI = (m_ucI + 1) % iKeyLen;
}
memcpy(m_aucState, m_aucState0, 256);
Javascript:
// buffer or array???
this.m_aucState0 = new Buffer(256)
this.m_aucState = new Buffer(256)
this.m_ucI
this.m_ucJ
this.m_pucState1 = []
this.m_pucState2 = []
for (var i = 0; i < 256; i++)
{
this.m_pucState1 = this.m_aucState0 + i
this.m_ucJ += this.m_pucState1[0] + (pucKeyData[0] + this.m_ucI)
this.m_pucState2 = this.m_aucState0 + this.m_ucJ
//Swaping
this.m_ucTemp = this.m_pucState1[0]
this.m_pucState1[0] = this.m_pucState2[0]
this.m_pucState2[0] = this.m_ucTemp
this.m_ucI = (this.m_ucI + 1) % iKeyLen
}
this.m_aucState.copy(this.m_aucState0, 0, 0, 256)
So my idea is because a pointer returns an address, that address contains the first byte of the pointer data. So if in an array I could just also point to the first index of the array right?
Is what I did above right?
Just for context let me add 1 function:
Javascript:
Crypt.prototype.setup = function(pucKeyData, iKeyLen) {
if (iKeyLen < 1)
throw new Error("Key Length should be at least 1")
var i;
for (i = 0; i < 256; i++)
this.m_aucState0[i] = i
this.m_ucI = 0
this.m_ucJ = 0
for (var i = 0; i < 256; i++)
{
this.m_pucState1 = this.m_aucState0 + i
this.m_ucJ += this.m_pucState1[i] + (pucKeyData[i] + this.m_ucI)
this.m_pucState2 = this.m_aucState0 + this.m_ucJ
//Swaping
this.m_ucTemp = this.m_pucState1[i]
this.m_pucState1[i] = this.m_pucState2[i]
this.m_pucState2[i] = this.m_ucTemp
this.m_ucI = (this.m_ucI + 1) % iKeyLen
}
this.m_aucState.copy(this.m_aucState0, 0, 0, 256)
//Initialize Indexes
this.m_ucI = 0
this.m_ucJ = 0
//Initialization Finished
this.m_bInit = true
}
CPP:
void CArcfourPRNG::SetKey(unsigned char *pucKeyData, int iKeyLen)
{
if(iKeyLen < 1)
throw exception("Key Length should be at least 1");
int i;
for(i=0; i<256; i++)
m_aucState0[i] = i;
m_ucI = 0;
m_ucJ = 0;
for(i=0; i<256; i++)
{
m_pucState1 = m_aucState0 + i;
m_ucJ += *m_pucState1 + *(pucKeyData+m_ucI);
m_pucState2 = m_aucState0 + m_ucJ;
//Swaping
m_ucTemp = *m_pucState1;
*m_pucState1 = *m_pucState2;
*m_pucState2 = m_ucTemp;
m_ucI = (m_ucI + 1) % iKeyLen;
}
memcpy(m_aucState, m_aucState0, 256);
//Initialize Indexes
m_ucI = 0;
m_ucJ = 0;
//Initialization Finished
m_bInit = true;
}
What is the difference of m_pucState1 and *m_pucState1 in this:
m_pucState1 = m_aucState + m_ucI;
m_ucJ += *m_pucState1;
In Javascript, there are typed buffer objects: http://www.javascripture.com/ArrayBuffer
You will also find something about the ctypes collection, but in my understanding they are used only for native OS library calls.
Also, I don't know a native JS Buffer object like you mention it. There is one in NodeJS, but I don't know its features.
If you insist of translating your code one-by-one, then these typed buffer objects may greatly support you. I think it's not a good way as while translating from C to Javascript, your terminology alters anyway. It alters from adding long pointer values to forming array indices.
Here is one problem example in your translation:
In C, you write:
m_ucJ += *m_pucState1 + *(pucKeyData+m_ucI);
In Javascript, you write:
this.m_ucJ += this.m_pucState1[0] + (pucKeyData[0] + this.m_ucI);
The brackets in the C term make m_ucI altering the address. So in Javascript this should rather be in the square brackets, somehow like this:
this.m_ucJ += this.m_pucState1[0] + pucKeyData[0 + this.m_ucI];
and then you can skip the "0 +". This shows how one-by-one translation between such different languages is full of traps.
So let's assume that we will use the simplest Javascript object, which is the array []. Then this is my suggestion. It's a draft, but it should give you a thorough idea:
// Define arrays
var aState0 = []; // m_aucState0
var aState = []; // m_aucState
// Define helpers
var state1Index; // *m_pucState1
var state2Index; // *m_pucState2
var i; // m_uci. There is no such thing as "uc" in Javascript.
var j; // m_ucj
var iLoop; // i in loop.
// It's readable to have this constant.
var bufferLength = 255;
// Somewhere we need:
var keyData;
var temp;
var iKeyLen;
// Just for here, give the array a size. So it's done in Javascript.
// Alternatively, fill it with 256 values from anywhere.
aState0[bufferLength] = 0;
// console.log(state0.length) will now print 256
// ...
// init i, j, iKeyLen ...
// ...
for (iLoop = 0; iLoop <= bufferLength; iLoop++) {
// This:
// m_pucState1 = m_aucState0 + i;
// m_ucJ += *m_pucState1 + *(pucKeyData+m_ucI);
// becomes:
state1Index = iLoop;
j += aState0[state1Index] + keyData[i];
// This:
// m_pucState2 = m_aucState0 + m_ucJ;
// becomes:
state2Index = j;
// This:
// m_ucTemp = *m_pucState1;
// *m_pucState1 = *m_pucState2;
// *m_pucState2 = m_ucTemp;
// becomes:
temp = aState0[state1Index];
aState0[state1Index] = aState0[state2Index];
aState0[state2Index] = temp;
// This:
// m_ucI = (m_ucI + 1) % iKeyLen;
// becomes:
i = (i+1) % iKeyLen;
}
// this:
// memcpy(m_aucState, m_aucState0, 256);
// would be a clone. So you'd need jQuery or else. But you can simply write:
for (index in state0) {
state[index] = state0[index];
}
Finally, you can drop j as it is equal to state2Index, and state1Index equal to iLoop.
But this is a puzzle where you will probably have to use paper and pencil and to draw some boxes and arrows to get clear with.
Hth :-)
So. I have 4 for loops inside other for loops in JS, and my code appears (FireBug agrees with me) that my code is syntactically sound, and yet it refuses to work. I'm attempting to calculate the key length in a vigenere cipher through the use of the Index of Coincidence, and Kappa tests <- if that helps any.
My main problem is that the task seems to be too computationally intensive for Javascript to run, as Firefox shoots up past 1GB of memory usage, and 99% CPU when I attempt to run the keylengthfinder() function. Any ideas of how to solve this problem, even if it takes much longer to calculate, would be greatly appreciated. Here's a link to the same code - http://pastebin.com/uYPBuZZz - Sorry about any indenting issues in this code. I'm having issues putting it on the page correctly.
function indexofcoincidence(text){
text = text.split(" ").join("").toUpperCase();
var textL = text.length;
var hashtable = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0];
var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
for (d=0; d<=25; d++) {
for (i=0; i < textL; i++){
if (text.charAt(i) === alphabet.charAt(d)){
hashtable[d] = hashtable[d] + 1;
}
}
}
var aa = hashtable[0]/textL;
var A = aa*aa;
var bb = hashtable[1]/textL;
var B = bb*bb;
var cc = hashtable[2]/textL;
var C = cc*cc;
var dd = hashtable[3]/textL;
var D = dd*dd;
var ee = hashtable[4]/textL;
var E = ee*ee;
var ff = hashtable[5]/textL;
var F = ff*ff;
var gg = hashtable[6]/textL;
var G = gg*gg;
var hh = hashtable[7]/textL;
var H = hh*hh;
var ii = hashtable[8]/textL;
var I = ii*ii;
var jj = hashtable[9]/textL;
var J = jj*jj;
var kk = hashtable[10]/textL;
var K = kk*kk;
var ll = hashtable[11]/textL;
var L = ll*ll;
var mm = hashtable[12]/textL;
var M = mm*mm;
var nn = hashtable[13]/textL;
var N = nn*nn;
var oo = hashtable[14]/textL;
var O = oo*oo;
var pp = hashtable[15]/textL;
var P = pp*pp;
var qq = hashtable[16]/textL;
var Q = qq*qq;
var rr = hashtable[17]/textL;
var R = rr*rr;
var ss = hashtable[18]/textL;
var S = ss*ss;
var tt = hashtable[19]/textL;
var T = tt*tt;
var uu = hashtable[20]/textL;
var U = uu*uu;
var vv = hashtable[21]/textL;
var V = vv*vv;
var ww = hashtable[22]/textL;
var W = ww*ww;
var xx = hashtable[23]/textL;
var X = xx*xx;
var yy = hashtable[24]/textL;
var Y = yy*yy;
var zz = hashtable[25]/textL;
var Z = zz*zz;
var Kappa = A+B+C+D+E+F+G+H+I+J+K+L+M+N+O+P+Q+R+S+T+U+V+W+X+Y+Z;
var Top = 0.027*textL;
var Bottom1 = 0.038*textL + 0.065;
var Bottom2 = (textL - 1)*Kappa;
var KeyLength = Top/(Bottom2 - Bottom1) ;
return Kappa/0.0385;
}
function keylengthfinder(text){
// Average Function Definition
Array.prototype.avg = function() {
var av = 0;
var cnt = 0;
var len = this.length;
for (var i = 0; i < len; i++) {
var e = +this[i];
if(!e && this[i] !== 0 && this[i] !== '0') e--;
if (this[i] == e) {av += e; cnt++;}
}
return av/cnt;
}
// Begin the Key Length Finding
var textL = text.length;
var hashtable = new Array(0,0,0,0,0,0,0,0,0,0,0,0);
for (a = 0; a <= 12; a++){ // This is the main loop, testing each key length
var stringtable = [];
for (z = 0; z <= a; z++){ // This allows each setting, ie. 1st, 4th, 7th AND 2nd, 5th, 8th to be tested
for (i = z; i < textL; i + a){
var string = '';
string = string.concat(text.charAt(i)); // Join each letter of the correct place in the string
stringtable[z] = indexofcoincidence(string);
}
}
hashtable[a] = stringtable.avg();
}
return hashtable;
}
Your problem is definitely right here
for (i = z; i < textL; i + a){
var string = '';
string = string.concat(text.charAt(i)); // Join each letter of the correct place in the string
stringtable[z] = indexofcoincidence(string);
}
Notice that if a=0 i never changes and therefore you are in an infinite loop.
Array.prototype.avg = function() {...}
should be only done once, and not every time keylengthfinder is called.
var Top = 0.027*textL;
var Bottom1 = 0.038*textL + 0.065;
var Bottom2 = (textL - 1)*Kappa;
var KeyLength = Top/(Bottom2 - Bottom1) ;
return Kappa/0.0385;
Why do you computer those variables if you don't use them at all?
var string = '';
string = string.concat(text.charAt(i)); // Join each letter of the correct place in the string
stringtable[z] = indexofcoincidence(string);
I don't know what you are trying to do in here. The string will always be only one character?
for (i = z; i < textL; i + a) {
...
stringtable[z] = ...
}
In this loop, you are computing values for i from z to textL - but you overwrite the same array item each time. So it would be enough to compute the stringtable[z] for i=textL-1 - or your algorithm is flawed.
A much shorter and more concise variant of the indexofcoincidence function:
function indexofcoincidence(text){
var l = text.replace(/ /g, "").length;
text = text.toUpperCase().replace(/[^A-Z]/g, "");
var hashtable = {};
for (var i=0; i<l; i++) {
var c = text.charAt(i);
hashtable[c] = (hashtable[c] || 0) + 1;
}
var kappa = 0;
for (var c in hashtable)
kappa += hashtable[c] * hashtable[c];
return kappa/(l*l)/0.0385;
}
All right. Now that we found your problem (including the infinite loop in case a=0, as detected by qw3n), let's rewrite the loop:
function keylengthfinder(text) {
var length = text.length,
probabilities = []; // probability by key length
maxkeylen = 13; // it might make more sense to determine this in relation to length
for (var a = 1; a <= maxkeylen; a++) { // testing each key length
var stringtable = Array(a); // strings to check with this gap
// read "a" as stringtable.length
for (var z = 0; z < a; z++) {
var string = '';
for (var i = z; i < textL; i += a) {
string += text.charAt(i);
}
// a string consisting of z, z+a, z+2a, z+3a, ... -th letters
stringtable[z] = string;
}
var sum = 0;
// summing up the coincidence indizes for current stringtable
for (var i=0; i<a; i++) {
sum += indexofcoincidence(stringtable[i]);
}
probabilities[a] = sum / a; // average
}
return probabilities;
}
Every of the loop statements has changed against your original script!
Never forget to declare the running variable to be local (var keyword)
a needs to start at zero - a key must have a minimum length of 1
to run from 1 to n, use i=1; i<=n; i++
to run from 0 to n-1, use i=0; i<n; i++ (nearly all loops, especially on zero-based array indizes).
Other loops than those two never occur in normal programs. You should get suspicious if you have loops from 0 to n or from 1 to n-1...
The update expression needs to update the running variable. i++ is a shortcut for i+=1 is a shortcut for i=i+1. Your expression, i + a, did not assign the new value (apart from the a=0 problem)!