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how to decode string in javascript?

I am trying to decode my string using JavaScript. Here is my code on JSBin.
decordMessage('oppeeennnn','1234');
function decordMessage(m,k) {
var msg = m.split('');
var keysplit = k.split('');
var str ='';
var j =0
for (var i=0;i<msg.length;){
str += msg[i];
if(j < keysplit.length -2 &&i < keysplit.length && keysplit[j]){
i = i + parseInt(keysplit[j]);
j++;
}
console.log(i +"i")
console.log(str);
}
console.log("after");
console.log(str);
}
I make a function in which message and key is passed.
Expected output :: open
Actually string charters are repeated in input message (encrypted message) using key. So I need to decode the message.

You forgot to put a break in the else condition, that's why it was looping infinitely till it ran out of memory. Run it in a browser and the tab will crash:
decordMessage('oppeeennnn','1234');
function decordMessage(m,k) {
var msg = m.split('');
var keysplit = k.split('');
var str ='';
var j =0
for (var i=0;i<msg.length;){
str += msg[i];
if(j < keysplit.length &&i < keysplit.length && keysplit[j]){
i = i + parseInt(keysplit[j]);
j++;
}
else
break;
}
console.log("after");
console.log(str); // prints open
}
By the way, a better way to write the loop would be:
function decordMessage(m,k) {
var msg = m.split('');
var keysplit = k.split('');
var str = '';
var j = 0, i = 0;
while (j < keysplit.length
&& i < msg.length) {
str += msg[i];
i += parseInt(keysplit[j]);
j++;
}
console.log(str)
}

This may helps you.
decordMessage('oppeeennnn', '1234');
function decordMessage(m, k) {
var arr = m.split("");
uniqueArray = arr.filter(function(item, pos) {
return arr.indexOf(item) == pos;
});
console.log(uniqueArray.join(""));
}
Assuming encryption logic goes as 123456....
Sample here

Simple Quiz Game JavaScript

I'm just learning now. Can you please help me, why am I not getting the correct output. This is my code:
//ask questions
var quiz = [
["When is Bulgaria established?", 681],
["What year was it before 16 years?", 2000],
["When does WWII ends?", 1945]
];
//variables
var answer = [];
var correct = [];
var wrong = [];
var correctAns = 0;
var wrongAns = 0;
var oList = "<ol>";
//function to print the result in ordered list
function printResult(result){
for(var j = 0; j < result.length; j++){
oList += "<li>" + result[i] + "</li>";
}
oList += "</ol>";
return oList;
}
function print(message) {
document.getElementById('output').innerHTML = message;
}
//looping, adding correct and wrong answeres
for(var i = 0; i < 3; i++) {
answer[i] = prompt(quiz[i][0]);
if(parseInt(answer[i]) == quiz[i][1]){
correct.push(quiz[i][0]);
correctAns++;
} else {
wrong.push(quiz[i][0]);
wrongAns++;
}
}
//print logic
if(correct.length < 1 || correct == undefined){
print("You did not guess any of the quiestions!");
} else if (correct.length >= 1){
print("You have guessed " + correctAns + " questions.");
print(printResult(correct));
print("You have " + wrongAns + " wrong answeres.");
if(wrongAns > 0){
print(printResult(wrong));
}
}
I have watched this code over and over again and I still can't understand why am I getting undefined as a result. In the debugger, after the loop I check my vars and everything seems ok.

In your printResult function you are using var i instead of j,
Also you better use innerHtml+=message;
//ask questions
var quiz = [
["When is Bulgaria established?", 681],
["What year was it before 16 years?", 2000],
["When does WWII ends?", 1945]
];
//variables
var answer = [];
var correct = [];
var wrong = [];
var correctAns = 0;
var wrongAns = 0;
//function to print the result in ordered list
function printResult(result){
//HERE:
var oList = "<ol>";
for(var j = 0; j < result.length; j++){
oList += "<li>" + result[j] + "</li>";
}
oList += "</ol>";
return oList;
}
function print(message) {
document.getElementById('output').innerHTML += message;
}
//looping, adding correct and wrong answeres
for(var i = 0; i < 3; i++) {
answer[i] = prompt(quiz[i][0]);
if(parseInt(answer[i]) == quiz[i][1]){
correct.push(quiz[i][0]);
correctAns++;
} else {
wrong.push(quiz[i][0]);
wrongAns++;
}
}
//print logic
if(correct.length < 1 || correct == undefined){
print("You did not guess any of the quiestions!");
} else if (correct.length >= 1){
print("You have guessed " + correctAns + " questions.");
print(printResult(correct));
print("You have " + wrongAns + " wrong answeres.");
if(wrongAns > 0){
print(printResult(wrong));
}
}
<div id="output">
</div>

Basically you have three problems.
reuse of oList, the variable should be inside declared and used only in printResult.
Inside of printResult, use of i where j have been used and
At print, you replace the actual content with new content.
Just a small hint with variable names for counting. It is good practise to start always with i instead of j and go on with the letters in the alphabet.
var quiz = [["When is Bulgaria established?", 681], ["What year was it before 16 years?", 2000], ["When does WWII ends?", 1945]],
answer = [],
correct = [],
wrong = [],
correctAns = 0,
wrongAns = 0;
//function to print the result in ordered list
function printResult(result) {
var oList = "<ol>"; // !!! move variable inside of the function
for (var j = 0; j < result.length; j++) {
oList += "<li>" + result[j] + "</li>"; // !!! use j indstead if i
}
oList += "</ol>";
return oList;
}
function print(message) {
document.getElementById('output').innerHTML += message; // !!! append message
}
//looping, adding correct and wrong answeres
for (var i = 0; i < 3; i++) {
answer[i] = prompt(quiz[i][0]);
if (parseInt(answer[i]) == quiz[i][1]) {
correct.push(quiz[i][0]);
correctAns++;
} else {
wrong.push(quiz[i][0]);
wrongAns++;
}
}
//print logic
if (correct.length < 1 || correct == undefined) {
print("You did not guess any of the quiestions!");
} else if (correct.length >= 1) {
print("You have guessed " + correctAns + " questions.");
print(printResult(correct));
print("You have " + wrongAns + " wrong answeres.");
if (wrongAns > 0) {
print(printResult(wrong));
}
}

Your main mistake is using i intead of j:
for(var j = 0; j < result.length; j++){
oList += "<li>" + result[j] + "</li>";// here was i before
}

Javascript Can't use array content as array index?

When I trird to run the js code, it always said "Uncaught TypeError: Cannot read property '_id' of undefined" for
deployedID.push(data[j]._id);
So after some thinking, I believe the problem lies in
var j = deploy[i];
Is there any way to solve it? Thanks in advance.
Below is the complete code:
var deploy = [];
var deployedID = [];
var deployedename = [];
var deployedoname = [];
var deployedrank = [];
function popularizeTable(){
$.get("/SSS/getlist", function(data){
deploy = randomunique(data.length ,100);
for (var i = 0; i < 100; i++){
var j = deploy[i];
deployedID.push(data[j]._id);
deployedename.push(data[j].ename);
deployedoname.push(data[j].oname);
deployedrank.push(data[j].rank);
}
var str = " ";
var k = 0;
for (var i = 0; i < 5; i++){
str += "<tr>";
for(var j = 0; j < 20; j++){
str += "<td><section id=\"" + deployedID[k] + "\" class=\"container\"><div class=\"card\">"
str += "<figure class=\"front\"><img src=\"images/back.jpg\"></figure>";
str += "<figure class=\"back\"><img src=\"images/Clear/" + deployedename[k] + "/001.jpg\"></figure></div></td></section>";
k++;
}
str += "</tr>";
}
$("#table").append(str);
});
}
$( document ).ready(function() {
popularizeTable();
$(document).on("mouseover", ".card", function(){
$(this).toggleClass("flipped")});
});
function randomunique(max, num){
var uniquelist = [];
for (var j = uniquelist.length; j < num; j++){
var i = parseInt(Math.random() * (max - 1) + 1);
if (uniquelist.indexOf(i) == -1){
uniquelist.push(i);
}
}
return uniquelist;
}

Javascript For Loop: Assignment to character not working

I was writing a test function to capitalize each word in a sentence. I ended up solving it; however, one of my first attempts to solve the problem didn't work when I thought it would.
function capSentence(str) {
var strArray = str.split(" ");
var answer = '';
var temp = '';
for(var i = 0; i < strArray.length; i++){
strArray[i][0] = strArray[i][0].toUpperCase();
answer += strArray[i];
if(i !== strArray.length-1){
answer += ' ';
}
}
return answer;
}
capSentence("this is a test");
I thought the above code would output "This Is A Test", but instead it outputs "this is a test".
strArray[i][0] = strArray[i][0].toUpperCase();
doesn't seem to have any affect. Why is that?

#thefourtheye's comment is correct. You need to build a new string.
function capSentence(str) {
var strArray = str.split(" ");
var answer = '';
var temp = '';
for(var i = 0; i < strArray.length; i++){
answer += strArray[i][0].toUpperCase();
answer += strArray[i].slice(1,strArray[i].length);
if(i !== strArray.length-1){
answer += ' ';
}
}
return answer;
}

Strings are immutable in Javascript. That's why you are not able to change the value of the strArray.
But you can do in this way:
function capSentence(str) {
strArray = str.split(" ");
console.log(strArray);
var answer = '';
var temp = '';
for(var i = 0; i < strArray.length; i++){
for (var j = 0; j< strArray[i].length; j++) {
if(j==0) {
temp = strArray[i][j].toUpperCase();
} else {
temp+=strArray[i][j];
}
}
answer += temp;
if(i !== strArray.length-1){
answer += ' ';
}
}
return answer;
}
This will retrun "This Is A Test"

Try this simple snippet,
function capSentence(str) {
var strArray = str.split(" ");
var answer = '';
var temp = '';
for(var i = 0; i < strArray.length; i++){
answer += (strArray[i].substring(0,1)).toUpperCase()+strArray[i].substring(1);
if(i !== strArray.length-1){
answer += ' ';
}
}
return answer;
}

Mccluskey algorithm, javascript

<html>
<body>
<script type="text/javascript">
start();
function start() {
var val = "0,1";
var n = 5;
var chars = ['a', 'b', 'c', 'd', 'e'];
gVars = chars.slice(0, n);
for (var i = 0; i < gVars.length; i++)
document.write(gVars[i] + "<br />");
var termsStr = val.split(',');
for (var i = 0; i < termsStr.length; i++)
document.write(termsStr[i] + "<br />");
var gOrigTerms = [];
var maxterm = Math.pow(2, termsStr.length) - 1;
document.write("maxterm: " + maxterm + "<br />");
for (var i = 0; i < termsStr.length; i++) {
gOrigTerms[i] = parseInt(termsStr[i]);
document.write(gOrigTerms[i] + "<br />");
if (gOrigTerms[i] > maxterm) document.write("Invalid term in term list." + "<br />");
}
gFormula = new Formula(gVars, gOrigTerms);
document.write(gFormula);
gFormula.toString();
gFormula.reduceToPrimeImplicants(); //here the breakpoint is inserted
}
function Formula(vars, terms)
{
this.vars = vars;
this.termList = [];
for (var i = 0; i < terms.length; i++) {
this.termList[i] = new Term(Dec2Bin(terms[i], vars.length));
document.write("this.termList" + this.termList[i] + "<br />");
}
this.orginalTermList = [];
document.write("this.orginalTermList" + this.orginalTermList + "<br />");
}
function Dec2Bin(dec, size) {
var bits = [];
for (var bit = 0; bit < size; bit++)
{
bits[bit] = 0;
}
var i = 0;
while (dec > 0)
{
if (dec % 2 == 0)
{
bits[i] = 0;
} else
{
bits[i] = 1;
}
i++;
dec = (dec / 2) | 0;
// Or with zero casts result to int (who knows why...)
}
bits.reverse();
return bits;
}
function Term(varVals)
{
this.varVals = varVals;
document.write("this.varVals: " + this.varVals);
}
function reduceToPrimeImplicants() //there is some problem with this function
{
this.originalTermList = this.termList.slice(0);
var numVars = this.termList[0].getNumVars();
var table = [];
for (var dontKnows = 0; dontKnows <= numVars; dontKnows++) {
table[dontKnows] = [];
for (var ones = 0; ones <= numVars; ones++) {
table[dontKnows][ones] = [];
}
table[dontKnows][numVars + 1] = [];
}
table[numVars + 1] = [];
table[numVars + 1][numVars + 1] = [];
for (var i = 0; i < this.termList.length; i++) {
var dontCares = this.termList[i].countValues(DontCare);
var ones = this.termList[i].countValues(1);
var len = table[dontCares][ones].length;
table[dontCares][ones][len] = this.termList[i];
}
for (var dontKnows = 0; dontKnows <= numVars - 1; dontKnows++) {
for (var ones = 0; ones <= numVars - 1; ones++) {
var left = table[dontKnows][ones];
var right = table[dontKnows][ones + 1];
var out = table[dontKnows + 1][ones];
for (var leftIdx = 0; leftIdx < left.length; leftIdx++) {
for (var rightIdx = 0; rightIdx < right.length; rightIdx++) {
var combined = left[leftIdx].combine(right[rightIdx]);
if (combined != null) {
if (out.indexOf(combined) < 0) {
var len = out.length;
out[len] = combined;
}
if (this.termList.indexOf(left[leftIdx]) >= 0) {
this.termList.splice(this.termList.indexOf(left[leftIdx]), 1);
}
if (this.termList.indexOf(right[rightIdx]) >= 0) {
this.termList.splice(this.termList.indexOf(right[rightIdx]), 1);
}
if (this.termList.indexOf(combined) < 0) {
var len = this.termList.length;
this.termList[len] = combined;
}
}
}
}
}
}
}
function getNumVars()
{
return this.varVals.length;
}
function countValues(value)
{
result = 0;
for (var i = 0; i < this.varVals.length; i++) {
if (this.varVals[i] == value) {
result++;
}
}
return result;
}
function combine(term)
{
var diffVarNum = -1; // The position where they differ
for (var i = 0; i < this.varVals.length; i++) {
{
if (this.varVals[i] != term.varVals[i])
if (diffVarNum == -1) {
diffVarNum = i;
} else { // They're different in at least two places return null; }
}
}
if (diffVarNum == -1)
{
// They're identical return null;
}
resultVars = this.varVals.slice(0);
resultVars[diffVarNum] = DontCare;
return new Term(resultVars);
}
</script>
</body>
</html>
In the above code, that is not complete, but which implements quine Mccluskey algorithm. There is a problem while it is debugged.
If a breakpoint is inserted at gFormula.reducetoPrimeImplicants(); the debugger does not go into that function. This is the last function called in the code until now. But, it does go to start(), which is the first function.
There is some problem in reducetoPrimeImplicants(); function because it also gives ERROR in internet explorer.
I am not able to figure out the error. If I remove reducetoPrimeImplicants(); function from the code the works fine.
Please, can somebody tell me why the debugger does not enter reducetoPrimeImplicants();.
I am using the Firebug debugger.
Thanks in advance.

The last function in your page combine() is missing a closing brace.
If you don't mind, a suggestion: Please use http://jsbeautifier.org/ or some similar tool to indent your code better.

Your For loop has two starting braces.
for (var i = 0; i < this.varVals.length; i++) {
{
So remove one. This should solve your problem.