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getting wrong answer for finding largest of 2 numbers using readline-sync in js [duplicate]

I store some parameters client-side in HTML and then need to compare them as integers. Unfortunately I have come across a serious bug that I cannot explain. The bug seems to be that my JS reads parameters as strings rather than integers, causing my integer comparisons to fail.
I have generated a small example of the error, which I also can't explain. The following returns 'true' when run:
console.log("2" > "10")

Parse the string into an integer using parseInt:
javascript:alert(parseInt("2", 10)>parseInt("10", 10))

Checking that strings are integers is separate to comparing if one is greater or lesser than another. You should always compare number with number and string with string as the algorithm for dealing with mixed types not easy to remember.
'00100' < '1' // true
as they are both strings so only the first zero of '00100' is compared to '1' and because it's charCode is lower, it evaluates as lower.
However:
'00100' < 1 // false
as the RHS is a number, the LHS is converted to number before the comparision.
A simple integer check is:
function isInt(n) {
return /^[+-]?\d+$/.test(n);
}
It doesn't matter if n is a number or integer, it will be converted to a string before the test.
If you really care about performance, then:
var isInt = (function() {
var re = /^[+-]?\d+$/;
return function(n) {
return re.test(n);
}
}());
Noting that numbers like 1.0 will return false. If you want to count such numbers as integers too, then:
var isInt = (function() {
var re = /^[+-]?\d+$/;
var re2 = /\.0+$/;
return function(n) {
return re.test((''+ n).replace(re2,''));
}
}());
Once that test is passed, converting to number for comparison can use a number of methods. I don't like parseInt() because it will truncate floats to make them look like ints, so all the following will be "equal":
parseInt(2.9) == parseInt('002',10) == parseInt('2wewe')
and so on.
Once numbers are tested as integers, you can use the unary + operator to convert them to numbers in the comparision:
if (isInt(a) && isInt(b)) {
if (+a < +b) {
// a and b are integers and a is less than b
}
}
Other methods are:
Number(a); // liked by some because it's clear what is happening
a * 1 // Not really obvious but it works, I don't like it

Comparing Numbers to String Equivalents Without Using parseInt
console.log(Number('2') > Number('10'));
console.log( ('2'/1) > ('10'/1) );
var item = { id: 998 }, id = '998';
var isEqual = (item.id.toString() === id.toString());
isEqual;

use parseInt and compare like below:
javascript:alert(parseInt("2")>parseInt("10"))

Always remember when we compare two strings.
the comparison happens on chacracter basis.
so '2' > '12' is true because the comparison will happen as
'2' > '1' and in alphabetical way '2' is always greater than '1' as unicode.
SO it will comeout true.
I hope this helps.

You can use Number() function also since it converts the object argument to a number that represents the object's value.
Eg: javascript:alert( Number("2") > Number("10"))

+ operator will coerce the string to a number.
console.log( +"2" > +"10" )

The answer is simple. Just divide string by 1.
Examples:
"2" > "10" - true
but
"2"/1 > "10"/1 - false
Also you can check if string value really is number:
!isNaN("1"/1) - true (number)
!isNaN("1a"/1) - false (string)
!isNaN("01"/1) - true (number)
!isNaN(" 1"/1) - true (number)
!isNaN(" 1abc"/1) - false (string)
But
!isNaN(""/1) - true (but string)
Solution
number !== "" && !isNaN(number/1)

The alert() wants to display a string, so it will interpret "2">"10" as a string.
Use the following:
var greater = parseInt("2") > parseInt("10");
alert("Is greater than? " + greater);
var less = parseInt("2") < parseInt("10");
alert("Is less than? " + less);

Write a fetch function which looks for a HTML text input element and returns its value

I have just started learning Javascript. I am doing the course in Viope World. I need to get two different numbers, but each time, I get the same number for the num and exponent variables, while the function calcPower is correct. I don't understand how to get different inputs in the function fetchValue() without having HTML for this task. I have tried using the method Document.querySelector() and other things which shouldn't be complicated for such an exercise.
These are the requirements:
Fill in the missing functions fetchValue(id) and calcPower(base, exponent). The function fetchValue(id) looks for a HTML text input element and returns its value. The function calcPower(base, exponent) has to calculate and return a number based on the values passed to it. Note that all of the printing happens within the pre-made section of the program.
This is the part of the code I can't change:
function calcFunc(){
var num = fetchValue("num");
var exponent = fetchValue("exponent");
console.log("The number " + num + "to the power of " + exponent + " is:");
console.log(calcPower(num, exponent));
}
My code:
function fetchValue(id){
let val = document.querySelector("input").value;
return val;
}
function calcPower(base, exponent){
var result = 1;
for(var counter=0; counter<exponent;counter++){
result*=base;
}
return result;
}

querySelector returns a reference to the first element of the given selector. See https://developer.mozilla.org/en-US/docs/Web/API/Document/querySelector. It is not the obvious way to fetch your values given that your function is set up to handle element ids.
Instead, individual elements with unique id can be referenced using document.getElementById("elementID") and you want the .value property of the element. See https://developer.mozilla.org/en-US/docs/Web/API/Document/getElementById.
To input values, the html needs some sort of input, you could use text or number inputs (both return strings, but the number input restricts entries to digits). The markup for these would be something like:
Number: <input type="number" id="inputValue"></input><br>
Exponent: <input type="number" id="inputExponent"></input>
Note the use of ids as attributes of the elements.
Javascript is a loosely typed language, meaning strict definition of variable types is not needed. This means that JS can make sensible calculations from 2*2 or "2"*"2" (both are calculated to be 4). However, it is good practice to formally convert string digits to numbers when you intend using them for calculations (not least because JS interprets "2"+"2" as "22" because + is both an arithmetic addition operator and a string concatenation operator so if you give it strings, JS assumes you want to concatenate them).
So, the fetchValue function could include the use of parseInt(string) to convert the input string values to numbers.
These principles are combined in the following working snippet to illustrate the approach:
function calcFunc(){
let num = fetchValue("inputValue");
let exponent = fetchValue("inputExponent");
console.log("The number " + num + " to the power of " + exponent + " is:");
console.log(calcPower(num, exponent));
}
function fetchValue(id){
return parseInt(document.getElementById(id).value);
}
function calcPower(base, exponent){
let result = 1;
for(let counter=0; counter<exponent;counter++){
result*=base;
}
return result;
}
input {
width: 3em;
}
Number: <input type="number" id="inputValue"></input><br>
Exponent: <input type="number" id="inputExponent"></input>
<p>
<button onclick="calcFunc()">process</button>

I hope this helps, If the exponent is negative, the result is 1 / (base^exponent). For example: 2^(-4) = 1 / (2^4) = 1 / 2 / 2 / 2 / 2. meaning the number 2 to the power of -4 is: 0.0625 and not 1
Math.abs is important here...
function fetchValue(id){
return document.getElementById(id).value;
}
function calcPower(base, exponent){
if (exponent == 0){
return 1;
}
else if(exponent < 0){
exponent = Math.abs(exponent);
return (1 / calcPower(base, exponent));
}
else if(exponent > 0){
return base * (calcPower(base,exponent - 1));
}
};

Append extra zeroes to decimal to make 4.5 look 4.500 but 4.5234 should be 4.5234

I have a value fetched from the database, it's like:
4.5 which should be 4.500
0.01 which should be 0.010
11 which should be 11.000
so I used this piece of code
sprintf("%.3f",(double)$html['camp_cpc'])
But here arised another problem. If $html['camp_cpc'] = '4.5234', then also it displays 4.523 instead of original value 4.5234
Also for other values with larger decimal like 0.346513, its only showing up to 0.346.
How can I solve this problem in JavaScript also?

Floats 4.5 and 4.500 correspond to the same number, so they cannot (and should not) be used/stored in a way that preserves the different representation. If you need to preserve the original representation given by a user, you need to store this field as a list (string) and convert to a float whenever you need the float value

In Javascript at least, this is an implementation of what I think you want:
function getValue(x, points) {
var str = x.toString();
// Convert to string
var idx = str.indexOf(".");
// If the number is an integer
if(!~idx) return str + "." + "0".repeat(points);
// Get the tail of the number
var end = str.substr(idx+1);
// If the tail exceeds the number of decimal places, return the full string
if(end.length > points) return str;
// Otherwise return the int + the tail + required number of zeroes
return str.substr(0, idx) + "." + end.substr(0, points) + "0".repeat(points-end.length);
}
console.log(getValue(4.5, 3)); //4.500
console.log(getValue(0.01, 3)); //0.010
console.log(getValue(11, 3)); //11.000
Working demo (Makes use of ES6 String.repeat for demonstration purposes)
The important thing to note here is that this is string manipulation. Once you start to say "I want the number to look like..." it's no longer a number, it's what you want to show the user.
This takes your number, converts it to the string and pads the end of the string with the appropriate number of zeroes. If the decimal exceeds the number of places required the full number is returned.

In PHP, use %0.3f — and you don't need to cast as (double)
<?php
echo sprintf("%0.3f", 4.5); // "4.500"
echo sprintf("%0.3f", 4.5234); // "4.523"
If you want to display 4 decimal places, use %0.4f
echo sprintf("%0.4f", 4.5); // "4.5000"
echo sprintf("%0.4f", 4.5234); // "4.5234"
To do this in JavaScript
(4.5).toFixed(3); // "4.500"

It could look sth. like this:
var n = [4.5234, 0.5, 0.11, 456.45];
var temp_n;
for(var i = 0; i < n.length; i++) {
temp_n = String(n[i]).split(".");
if(temp_n[1] == null || temp_n[1].length < 3) {
n[i] = n[i].toFixed(3);
}
}

format decimal in javascript

i would like to format decimal values to specific format as like
1.23 should be shown as 0001.23 using javascript. is there any specific functions like toPrecision(), tofixed() in javascript to handle these kind of formatting or any pointers to go ahead with any solutions?
here preceeding decimal is dynamic one.
for example :
i have 2 values :
first value : 99.4545
second value : 100.32
in this second value has higher length (3)before decimal and first value has higher length after decimal(4). so subtracted result(0.8655) of this should be formatted as ###.#### (000.8685)
thank you

Just make a function that does what you want it to. Here is an example you can expand on if you want.
function pad(num, padSize){
var numString = "" + num.split('.')[0];
if(num.length < padSize){
var numZeroes = padSize-num.length;
var zeroes = "";
while(numZeroes){zeroes += "0"; numZeroes--;}
return zeroes + num;
}else return num;
}

if you want to lpad some 0 onto 1.23 you can do the following
var value = 1.23
value = ("0000000"+ value).slice(-7);
Change the -7 to be whatever you want the total string length including the decimal point to be.
Added after question edit
The above should handle your question pre-edit but for the rest of it you'll need something like this.
var formatNum = function (num, preLen, postLen) {
var value = num.split("."),
padstring = "0";
padLen = (preLen > postLen)?preLen:postLen;
for (i = 0; i < padLen; i++) {
padstring += padstring;
}
if (typeof(value[1]) === "undefined") {
value[1] = "0";
}
return ((padstring + value[0]).slice(-preLen)+ "." + (value[1] + padstring).substring(0,postLen));
}
This takes the number you want formatted and the lengths you want each string to be on either side of the '.'. It also handles the case of an integer.
If you want it to output any other cases such as returning an integer, you'll have to add that in.

Try to use a string, like "000" + some value

using the digits of a number as an array

var number = 342345820139586830203845861938475676
var output = []
var sum = 0;
while (number) {
output.push(number % 10);
number = Math.floor(number/10);
}
output = output.reverse();
function addTerms () {
for (i = 0; i < output.length; i=i+2) {
var term = Math.pow(output[i], output[i+1]);
sum += term;
}
return sum;
}
document.write(output);
document.write("<br>");
document.write(addTerms());
I am trying to take that large number and split it into its digits. Then, find the sum of the the first digit raised to the power of the 2nd, 3rd digit raiseed to the 4th, 5th raised to the 6th and so on. for some reason, my array is returning weird digits, causing my sum to be off. the correct answer is 2517052. Thanks

You're running into precision issues within JavaScript. Just evaluate the current value of number before you start doing anything, and the results may surprise you:
>>> var number = 342345820139586830203845861938475676; number;
3.423458201395868e+35
See also: What is JavaScript's highest integer value that a Number can go to without losing precision?
To resolve your issue, I'd store your input number as an array (or maybe even a string), then pull the digits off of that.
This will solve your calculation with the expected result of 2517052:
var number = "342345820139586830203845861938475676";
var sum = 0;
for(var i=0; i<number.length; i=i+2){
sum += Math.pow(number.charAt(i), number.charAt(i+1));
}
sum;

JavaScript stores numbers in floating point format (commonly double). double can store precisely only 15 digits.
You can use string to store this large number.

As mentioned, this is a problem with numeric precision. It applies to all programming languages that use native numeric formats. Your problem works fine if you use a string instead
var number = '342345820139586830203845861938475676'
var digits = number.split('')
var total = 0
while (digits.length > 1) {
var [n, power] = digits.splice(0, 2)
total += Math.pow(n, power)
}
(the result is 2517052, byt the way!)

Cast the number as a string and then iterate through it doing your math.
var number = "342345820139586830203845861938475676";//number definition
var X = 0;//some iterator
var numberAtX = 0 + number.charAt(X);//number access

The greatest integer supported by Javascript is 9007199254740992. So that only your output is weird.
For Reference go through the link http://ecma262-5.com/ELS5_HTML.htm#Section_8.5

[edit] adjusted the answer based on Borodins comment.
Mmm, I think the result should be 2517052. I'd say this does the same:
var numbers = '342345820139586830203845861938475676'.split('')
,num = numbers.splice(0,2)
,result = Math.pow(num[0],num[1]);
while ( (num = numbers.splice(0,2)) && num.length ){
result += Math.pow(num[0],num[1]);
}
console.log(result); //=> 2517052

The array methods map and reduce are supported in modern browsers,
and could be worth defining in older browsers. This is a good opportunity,
if you haven't used them before.
If you are going to make an array of a string anyway,
match pairs of digits instead of splitting to single digits.
This example takes numbers or strings.
function sumPower(s){
return String(s).match(/\d{2}/g).map(function(itm){
return Math.pow(itm.charAt(0), itm.charAt(1));
}).reduce(function(a, b){
return a+b;
});
}
sumPower('342345820139586830203845861938475676');
alert(sumPower(s))
/*
returned value:(Number)
2517052
*/