How to convert hex to decimal WITH A LOOP in JavaScript

Question

Is it possible to convert a hex number to a decimal number with a loop?

Example: input "FE" output "254"

I looked at those questions :

How to convert decimal to hex in JavaScript?

Writing a function to convert hex to decimal Writing a function to convert hex to decimal

Writing a function to convert hex to decimal

How to convert hex to decimal in R

How to convert hex to decimal in c#.net?

And a few more that were not related to JS or loops. I searched for a solution in other languages too in case that I find a way to do it,but I didn't. The first one was the most useful one. Maybe I can devide by 16,compare the result to preset values and print the result, but I want to try with loops. How can I do it?

Answer 1

Maybe you are looking for something like this, knowing that it can be done with a oneliner (with parseInt )?

 function hexToDec(hex) { var result = 0, digitValue; hex = hex.toLowerCase(); for (var i = 0; i < hex.length; i++) { digitValue = '0123456789abcdef'.indexOf(hex[i]); result = result * 16 + digitValue; } return result; } console.log(hexToDec('FE'));

Alternative

Maybe you want to have a go at using reduce , and ES6 arrow functions :

 function hexToDec(hex) { return hex.toLowerCase().split('').reduce( (result, ch) => result * 16 + '0123456789abcdefgh'.indexOf(ch), 0); } console.log(hexToDec('FE'));

Answer 2

Just another way to do it...

 // The purpose of the function is to convert Hex to Decimal. // This is done by adding each of the converted values. function hextoDec(val) { // Reversed the order because the added values need to 16^i for each value since 'F' is position 1 and 'E' is position 0 var hex = val.split('').reverse().join(''); // Set the Decimal variable as a integer var dec = 0; // Loop through the length of the hex to iterate through each character for (i = 0; i < hex.length; i++) { // Obtain the numeric value of the character A=10 B=11 and so on.. // you could also change this to var conv = parseInt(hex[i], 16) instead var conv = '0123456789ABCDEF'.indexOf(hex[i]); // Calculation performed is the converted value * (16^i) based on the position of the character // This is then added to the original dec variable. 'FE' for example // in Reverse order [E] = (14 * (16 ^ 0)) + [F] = (15 * (16 ^ 1)) dec += conv * Math.pow(16, i); } // Returns the added decimal value return dec; } console.log(hextoDec('FE'));

Answer 3

If you want to loop over every hex digit, then just loop from end to beginning, shifting each digit 4 bits to the left as you add them (each hex digit is four bits long):

function doit(hex) {
    var num = 0;
    for(var x=0;x<hex.length;x++) {
        var hexdigit = parseInt(hex[x],16);
        num = (num << 4) | hexdigit;
    }
    return num;
}

Answer 4

Sorry that was backwards, and I can't find where to edit answer, so here is corrected answer:

function doit(hex) {
    var num = 0;
    for(var x=0;x<hex.length;x++) {
        var hexdigit = parseInt(hex[x],16);
        num = (num << 4) | hexdigit;
    }
    return num;
}

Answer 5

JavaScript can natively count in hex. I'm finding out the hard way that, in a loop, it converts hex to decimal, so for your purposes, this is great.

prepend your hex with 0x , and you can directly write a for loop.

For example, I wanted get an array of hex values for these unicode characters, but I am by default getting an array of decimal values.

Here's sample code that is converting unicode hex to dec

    var arrayOfEmojis = [];

    // my range here is in hex format
    for (var i=0x1F600; i < 0x1F64F; i++) {
        arrayOfEmojis.push('\\u{' + i + '}');
    }

    console.log(arrayOfEmojis.toString()); // this outputs an array of decimals