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JavaScript program to convert binary to decimal

I am trying to make a program which is able to do both decimal to binary and binary to decimal conversions.
I am having trouble with the binary to decimal portion of the code. Forgive me as I know the coding is quite incomplete but I can't figure out where I am going wrong.
Currently I am getting partially correct output in the calculation field (ex. "there is a 1 in the value of (2^0)" and "there is a 2 in the value of (2^1)").
However, when I type 11 as decimal the calculation field is repeating the code twice
(ex. "there is a 1 in the value of (2^0)","there is a 2 in the value of (2^1)","there is a 1 in the value of (2^0)", "there is a 2 in the value of (2^1)").
Obviously it should only give those values once per number.
Also the output field for the actual binary number is incorrect as well, and some of the variables aren't utilized/not needed, but I have been trying to fix the problem of repeating values first before I worked on that.
Any help would be much appreciated!!
function convertByArray(bval) {
var rB = new Array();
var outstr = "";
var p, t, a, o;
o = 0;
for(var i=0; i<bval.length; i++) {
var b = bval.charCodeAt(i);
t = 2;
p = i;
a = t ** p;
if(a === t ** p) {
outstr += a;
}
var bV = b;
$("txtCalc").value += "There is a " + a + " in the value " + "(" + t + "^" + p + ")" + "\n";
o += 1;
b = bV;
$("txtOut").value = outstr;
}
}

You can simply your code if you access the most-significant bit of the bit-string by taking the length (minus one) and subtracting it from the current position. You can access string characters like an array.
var $txtCalc = $(".txtCalc");
var $txtOut = $(".txtOut");
binaryToDecimal("10010101"); // 149
function binaryToDecimal(bval) {
var base = 2, result = 0;
for (var pos = 0; pos < bval.length; pos++) {
var bit = +bval[(bval.length - 1) - pos];
if (bit === 1) {
result += base ** pos;
}
var message = "There is a " + bit + " in the position (" + base + "^" + pos + ")";
$txtCalc.val($txtCalc.val() + message + "\n");
}
$txtOut.val(result);
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input class="txtOut" />
<br />
<textarea class="txtCalc" rows="10" cols="60"></textarea>
Alternatively, you can simply your program to the following. In JavaScript, you can parse any number in any base and format to another base.
var $txtOut = $(".txtOut");
binaryToDecimal("10010101"); // 149
function convertFromBaseToBase(number, fromBase, toBase) {
return parseInt(number, fromBase).toString(toBase);
}
function binaryToDecimal(bval) {
$txtOut.val(convertFromBaseToBase(bval, 2, 10));
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input class="txtOut" />

How to return data from a function

I'm trying to solve the following Kata:
a 2 digit number, if you add the digits together, multiply by 3, add 45 and reverse.
I'm unable to figure out how to return the data from my function so that I can later assign the value to an HTML element.
This is my code.
function daily() {
for(var j = 10; j < 100; j++) {
function teaser(num) {
var x = num;
var y = x.toString().split("");
if(y.length == 2) {
var sum = parseInt(y[0]) + parseInt(y[1]);
if(sum * 3 == x) {
console.log(x + " is equal to 3 times " + sum);
var addFortyFive = x + 45;
console.log("Adding 45 to " + x + " gives " + addFortyFive);
var reversal = parseInt(addFortyFive.toString().split('').reverse().join(''));
console.log("'The 2 digit number " + x + ", is 3 times the sum (" + sum + ") of its digits. If 45 is added to " + x + ", the result is " + addFortyFive + ". If the digits are reversed, the number is... " + reversal + ".");
}
} else {
console.log("Not a 2 digit Number!!");
}
}
teaser(j);
}
}

From your question I'm guessing you need reversal value on function daily for loop.
Would recommend you to take out function teaser from inside for-loop, this will make code much cleaner and easy to understand and you can do like:
function daily() {
for(var j = 10; j < 100; j++) {
var teaser = teaser(j);
// Can now use anything returned from teaser function here
}
}
function teaser(num) {
var x = num;
var y = x.toString().split("");
if(y.length == 2) {
var sum = parseInt(y[0]) + parseInt(y[1]);
if(sum * 3 == x) {
console.log(x + " is equal to 3 times " + sum);
var addFortyFive = x + 45;
console.log("Adding 45 to " + x + " gives " + addFortyFive);
var reversal = parseInt(addFortyFive.toString().split('').reverse().join(''));
console.log("'The 2 digit number " + x + ", is 3 times the sum (" + sum + ") of its digits. If 45 is added to " + x + ", the result is " + addFortyFive + ". If the digits are reversed, the number is... " + reversal + ".");
return reversal;
}
} else {
console.log("Not a 2 digit Number!!");
return false;
}
}
If don't want to take function out then you can do this:
function daily() {
for(var j = 10; j < 100; j++) {
function teaser(num) {
var x = num;
var y = x.toString().split("");
if(y.length == 2) {
var sum = parseInt(y[0]) + parseInt(y[1]);
if(sum * 3 == x) {
console.log(x + " is equal to 3 times " + sum);
var addFortyFive = x + 45;
console.log("Adding 45 to " + x + " gives " + addFortyFive);
var reversal = parseInt(addFortyFive.toString().split('').reverse().join(''));
console.log("'The 2 digit number " + x + ", is 3 times the sum (" + sum + ") of its digits. If 45 is added to " + x + ", the result is " + addFortyFive + ". If the digits are reversed, the number is... " + reversal + ".");
return reversal;
}
} else {
console.log("Not a 2 digit Number!!");
return false;
}
}
var teaser = teaser(j);
// Can now use anything returned from teaser function here
}
}

Returning something from a function is very simple!
Just add the return statement to your function.
function sayHello(name) {
return 'Hello ' + name + '!';
}
console.log(sayHello('David'));

okay, so my issue has been solved! Thanks all of you, especially krillgar, so I had to alter the code you gave me krillgar, a little bit in order to populate the results array with only the numbers (one number in this case) that satisfy the parameters of the daily tease I was asking about. yours was populating with 89 undefined and on number, 27 because it is the only number that works.
One of my problems was that I was expecting the return statement to not only save a value, but also show it on the screen, but what I was not realizing was that I needed a place to store the value. In your code you created a result array to populate with the correct numbers. And also, I needed a variable to store the data for each iteration of the for loop cycling through 10 - 100. Anyways, you gave me what I needed to figure this out and make it do what I wanted it to do, and all is well in the world again.
Anyway, thank you all for your help and input, and I will always remember to make sure I have somewhere to store the answers, and also somewheres to store the value of each loop iteration in order to decide which numbers to push into the results array and save it so it can be displayed and/or manipulated for whatever purpose it may be. I guess I was just so busy thinking about the fact that when I returned num it didn't show the value, instead of thinking about the fact that I needed to store the value. Here is the final code for this problem and thanks again peoples!
function daily() {
var results = [];
for(var j = 10; j < 100; j++) {
function teaser(num) {
var x = num;
var y = x.toString().split("");
if(y.length == 2) {
var sum = parseInt(y[0]) + parseInt(y[1]);
if(sum * 3 == x) {
console.log(x + " is equal to 3 times " + sum);
var addFortyFive = x + 45;
console.log("Adding 45 to " + x + " gives " + addFortyFive);
var reversal = parseInt(addFortyFive.toString().split('').reverse().join(''));
console.log("'The 2 digit number " + x + ", is 3 times the sum (" + sum + ") of its digits. If 45 is added to " + x + ", the result is " + addFortyFive + ". If the digits are reversed, the number is... " + reversal + ".");
return num;
// Here you have one that is correct, so return it:
} else {
console.log(num + " does not fulfill function parameters");
// This is just so you can visualize the numbers
return null;
}
}
}
var answer = teaser(j);
if(answer != null) {
results.push(answer);
}
}
return results;
}

As was said in the comments of the question, because you're going to (most likely) have multiple answers that match your condition, you will need to store those in an array. Your teaser function returns individual results, where daily will check all the numbers in your range.
function daily() {
var results = [];
for(var j = 10; j < 100; j++) {
function teaser(num) {
var x = num;
var y = x.toString().split("");
if(y.length == 2) {
var sum = parseInt(y[0]) + parseInt(y[1]);
if(sum * 3 == x) {
console.log(x + " is equal to 3 times " + sum);
var addFortyFive = x + 45;
console.log("Adding 45 to " + x + " gives " + addFortyFive);
var reversal = parseInt(addFortyFive.toString().split('').reverse().join(''));
console.log("'The 2 digit number " + x + ", is 3 times the sum (" + sum + ") of its digits. If 45 is added to " + x + ", the result is " + addFortyFive + ". If the digits are reversed, the number is... " + reversal + ".");
// Here you have one that is correct, so return it:
return num;
} else {
// Make sure we don't return undefined for when the sum
// times three doesn't equal the number.
return null;
}
} else {
console.log("Not a 2 digit Number!!");
return null;
}
}
var answer = teaser(j);
if (answer !== null) {
results.push(answer);
}
}
return results;
}

How to return a String representation of a calculation in Javascript

I am currently trying to complete an assignment for an intro2Javascript course. The question basically asks me to return a string of multiples of 2 parameters (num, numMultiple). Each time it increments the value i until i = numMultiple. For example:
5 x 1 = 5\n
5 x 2 = 10\n
5 x 3 = 15\n
5 x 4 = 20\n
This was my attempt:
function showMultiples(num, numMultiples) {
var result;
for (i = 1; i <= numMultiples; i++) {
result = num * i
multiples = "" + num + " x " + i + " = " + result + "\n"
return (multiples)
}
}
...and because the assignment comes with pre-written console logs:
console.log('showMultiples(2,8) returns: ' + showMultiples(2, 8));
console.log('showMultiples(3,2) returns: ' + showMultiples(3, 2));
console.log('showMultiples(5,4) returns: ' + showMultiples(5, 4));
console.log('\n');
This is my output:
showMultiples(2,8) returns: 2 x 1 = 2
Scratchpad/1:59:1
showMultiples(3,2) returns: 3 x 1 = 3
Scratchpad/1:60:1
showMultiples(5,4) returns: 5 x 1 = 5
UPDATE

You were doing two things incorrectly:
1) You were returning after the first iteration through your loop
2) You were assigning to multiples instead of appending to it.
Since you want to gather all the values and then show the final result first, I add all of the values to an array, and then use unshift() to add the final element (the result) to the beginning of the array. Then I use join() to return a string representation of the desired array.
function showMultiples(num, numMultiples) {
var result;
var multiples = [];
for (let i = 1; i <= numMultiples; i++) {
result = num * i
multiples.push("" + num + " x " + i + " = " + result + "\n")
}
multiples.unshift(multiples[multiples.length-1]);
return (multiples.join(''))
}
console.log('showMultiples(2,8) returns: ' + showMultiples(2, 8));
console.log('showMultiples(3,2) returns: ' + showMultiples(3, 2));
console.log('showMultiples(5,4) returns: ' + showMultiples(5, 4));
console.log('\n');

You need to declare all variables, because without you get global variables (beside that it does not work in 'strict mode').
The second point is to use multiples with an empty string for collecting all intermediate results and return that value at the end of the function.
For keeping the last result, you could use another variable and append that value at the end for return.
function showMultiples(num, numMultiples) {
var i,
result,
multiples = "",
temp = '';
for (i = 1; i <= numMultiples; i++) {
result = num * i;
temp = num + " x " + i + " = " + result + "\n";
multiples += temp;
}
return temp + multiples;
}
console.log('showMultiples(2,8) returns: ' + showMultiples(2, 8));
console.log('showMultiples(3,2) returns: ' + showMultiples(3, 2));
console.log('showMultiples(5,4) returns: ' + showMultiples(5, 4));

As other answers say, your problem is in multiple.
You are clearing multiple every iteration and storing the new value, but you do not want that, you want to add the new result, and to do so you use this code:
multiples = multiple + "" + num + " x " + i + " = " + result + "\n"
which can be compressed in what the rest of the people answered:
multiples += "" + num + " x " + i + " = " + result + "\n"
Probably you already know, but to ensure:
a += b ---> a = a + b
a -= b ---> a = a - b
a *= b ---> a = a * b
and there are even more.

the multiplication of a code between two numbers incorrectly outputting number

function showMultiples(num, numMultiples){
for(i=1; i<=numMultiples; i++){
var multiple = num + " x " + i + " = " + num * i;
}
return multiple;
}
console.log('showMultiples(2,8) returns: ' + showMultiples(2,8));
For this code, what the function should do is, by looking at num and numMultiples variable, it should give you the list of multiplication that is possible with the two numbers. Therefore the console should print out
2x1=2 2x2=4 2x3=6 2x4=8 2x5=10 2x6=12 2x7=14 2x8=16
However, this code prints out 2x8 = 16 any guess to why?

You're assigning the value to multiple then returning it in the end, when your loop has finished, meaning multiple will be 2x8. If you do a console.log(multiple) right under var multiple = num + " x " + i + " = " + num * i; you will see it print out correctly.
EDIT:
function showMultiples(num, numMultiples){
var result = [];
for(i=1; i<=numMultiples; i++){
result.push(num + " x " + i + " = " + num * i);
}
return result.join(' ');
}
Add results to an array and when the function completes, join the values inside the array and return the results.

You only have one print statement, and that is outside of the loop. If you want to print multiple times, you need to put the print statement inside of the loop, something like this:
function showMultiples(num, numMultiples) {
console.log(`showMultiples(${num}, ${numMultiples}) returns:`);
Array.from({length: numMultiples}, (v, k) => k + 1).
forEach(i => console.log(`${num}×${i} = ${num * i}`));
}
showMultiples(2, 8)
// showMultiples(2, 8) returns:
// 2×1 = 2
// 2×2 = 4
// 2×3 = 6
// 2×4 = 8
// 2×5 = 10
// 2×6 = 12
// 2×7 = 14
// 2×8 = 16
However, that is bad design. You shouldn't mix data transformation and I/O. It is much better to separate the two and build the data up first completely, then print it:
function showMultiples(num, numMultiples) {
return Array.from({length: numMultiples}, (v, k) => k + 1).
map(i => `${num}×${i} = ${num * i}`).
join(", ");
}
console.log(`showMultiples(2, 8) returns: ${showMultiples(2, 8)}`);
// showMultiples(2, 8) returns: 2×1 = 2, 2×2 = 4, 2×3 = 6, 2×4 = 8, 2×5 = 10, 2×6 = 12, 2×7 = 14, 2×8 = 16
This is much more idiomatic ECMAScript.

JavaScript - concat two numbers and treat the result as a number [duplicate]

This question already has answers here:
How to convert a string to an integer in JavaScript
(32 answers)
Closed 6 years ago.
here's the code I'm struggling with. I'd like to concat the two inputs together and keep the result as an integer (number in JS's case).
var secsVal = -1;
function valueAssign(i) {
if (secsVal == -1){
document.getElementById("countdown").value = i;
document.getElementById("countdown").innerHTML = (i);
secsVal = i;
}
else {
secsVal = "" + secsVal + i;//concatenating first value of i to the second.
secsVal = secsVal.map(Number);//trying to convert back to num, but I think map() needs to see an array, which I don't think I got here.
document.getElementById("countdown").value = secsVal;
document.getElementById("countdown").innerHTML = (secsVal);//I want to replace the first displayed digit here, with the new (concatenated) number.
}
}

It makes no sense to use a number for a value in an input tag. The type is always a string.
To convert to number use either Number or an unary +
secsVal = Number(secsVal);
or
secsVal = +secsVal;

Try this
secsVal = +("" + secsVal + i);

secsVal = Number('' + secsVal + i) // explicit cast to number
secsVal = +('' + secsVal + i) // implicit cast to number
secsVal = parseInt('' + secsVal + i) // explicit cast to integer
secsVal = ~~('' + secsVal + i) // implicit cast to integer

Simply use +secsVal
var secsVal = -1;
function valueAssign(i) {
if (secsVal == -1){
document.getElementById("countdown").value = i;
document.getElementById("countdown").innerHTML = (i);
secsVal = i;
}
else {
secsVal = "" + secsVal + i;
console.log(typeof secsVal);//secsVal is a string
secsVal = +secsVal;
console.log(typeof secsVal); //secsVal is now a number
document.getElementById("countdown").value = secsVal;
}
}
<input type="number" id="countdown"/>
<button onclick="valueAssign(5)">Click</button>

How about parsing the String?
"The parseInt() function parses a string and returns an integer."
http://www.w3schools.com/jsref/jsref_parseint.asp