JavaScript hex2bin实现

Question

I tried to implement a JS analogue of PHP's hex2bin . I found a few versions of hex2bin in JS, but all of these show the same result, which is different from the PHP result.

For example, a string 440EF96DB9A2225C32E031659DF2608B49932F0D8AFAC46F74FA56FF3E1AE952 looks like this:

As I can see, the results are very similar, but still different. What can be wrong?

Answer 1

Nothing is wrong. The results are the same, but strings are visualised differently. PHP and JavaScript output certain characters differently. Take for instance the character with code point 249:

echo chr(249);
// Equivalent to 
echo hex2bin("F9");

The output is " ".

While in JavaScript the output of the same character is "ù":

 console.log(String.fromCharCode(249)); 

Other characters may not be visible at all in one, but visible in the other. Both languages differ in internal character encoding which may also play a role in their rendering of strings.

If you want to ensure that they are the same, then represent the hex2bin output in base64 encoding:

In PHP ( base64_encode ):

base64_encode(hex2bin("440EF96DB9A2225C32E031659DF2608B49932F0D8AFAC46F74FA56FF3E1AE952"));

In JavaScript ( btoa ):

 const hex2bin = s => s.match(/../g).map(c => String.fromCharCode(parseInt(c, 16))).join``; console.log(btoa(hex2bin("440EF96DB9A2225C32E031659DF2608B49932F0D8AFAC46F74FA56FF3E1AE952"))); 

Both output:

RA75bbmiIlwy4DFlnfJgi0mTLw2K+sRvdPpW/z4a6VI=