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.
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1That's what I'd expect to happen. What are you expecting this to do that it doesn't do?greg84– greg842013-04-21 15:39:22 +00:00Commented Apr 21, 2013 at 15:39
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To convert 32 as a string that displays the binary number!Ken– Ken2013-04-21 15:41:28 +00:00Commented Apr 21, 2013 at 15:41
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5 Answers
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
9 Comments
Ken
So this does the same right? It converts the string 32 into an integer and then do the binary conversion..
Shai UI
why not just decnum.toString(2) without all the foreplay
Andbdrew
@foreyez because
prompt returns a String, and String::toString doesn't take a radixShai UI
I mean "var decnum=123; alert(decnum.toString(2));"
Andbdrew
@foreyez sure, that'll work. The question is about a string (that just happens to called
num) though. |
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;
}
Comments
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.
Comments
/** 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));
Comments
Cast it to an integer first. At the moment you're converting a string to it's binary representation.
num = +num;
2 Comments
christopher
Convert it to an int. Then Javascript can convert it to a binary string.
christopher
Okay. please mark either of the answers as correct. Glad we could help.