String Conversion in Javascript (Decimal to Binary)

Question

A newbie here! Wondering why the following conversion fails!

var num = prompt("Enter num");
alert(num.toString(2));

If num input is 32. I get 32 as num alert message too.

Answer 1

try

(+num).toString(2)

,

Number(num).toString(2)

or

parseInt(num, 10).toString(2)

Any of those should work better for you.

The issue is that the toString method of javascript Number objects overrides the toString method of Object objects to accept an optional radix as an argument to provide the functionality you are looking for. The String object does not override Object's toString method, so any arguments passed in are ignored.

For more detailed information about these objects, see the docs at Mozilla:

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Number/toString https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String#Methods

or W3 schools:

http://www.w3schools.com/jsref/jsref_tostring_number.asp http://www.w3schools.com/jsref/jsref_obj_string.asp

Answer 2

With this function you can specify length of the output.

For example decbin(7,4) produces 0111.

function decbin(dec,length){
  var out = "";
  while(length--)
    out += (dec >> length ) & 1;    
  return out;  
}

demo

Answer 3

Here is my solution that does not use parseInt, but rather a method that shows the logic behind the conversion of decimal to binary.

This method prints the bits to the array which you may later print out if you wish:

var number = 156;
var converted = [];

while(number>=1) {
    converted.unshift(number%2);
    number = Math.floor(number/2);
}

The converted array will now appear like so:

[1,0,0,1,1,1,0,0]

which of course converts back to 156.

Answer 4

/** Convert a decimal number to binary **/

var toBinary = function(decNum){
    return parseInt(decNum,10).toString(2);
}

/** Convert a binary number to decimal **/

var toDecimal = function(binary) {
    return parseInt(binary,2).toString(10);
}

Finally use it

var num= prompt("Enter num"); 
alert(toBinary(num));

Answer 5

Cast it to an integer first. At the moment you're converting a string to it's binary representation.

num = +num;