JavaScript：在字符串中转义％d

Question

I've got the following code in Node.js:

var str = '',
    ch;

for(/*standard for loop*/){
 // some code ...

 ch = '%' + buffer[i].toString(16);

 str += ch;
} 

Now when buffer[i].toString(16) returns, let's say d6 , resulting string doesn't contain %d6 , but NaN6 instead.

Now I know %d is used in C's sprinf, but afaik JavaScript nor Node has sprintf or equivalent function.

I need %d6 in my string, so what can I do to prevent JS from automatically converting %d (and others, like %f ) to NaN?

Answer 1

You cannot use toString method for your own purproses, because JS already has own function with that name.

1. Update firefox to newest version. Also make sure you are using firefox.
2. I tested and your solution should work. Please alert() everything.

What is the output of:

ch = '%' + buffer[i].toString(16);
alert(ch);
alert(buffer[i]);
alert(buffer[i].toString(16));

Answer 2

The error is not in the code you pasted, if we do a quick test:

function test()
{
  var stuff = 214;
  var str = '', ch;

  ch = '%' + stuff.toString(16);
  alert(ch);
} 

we see that what we want to be returned is in fact returned (%d6).

NaN stands for not a number, are you sure what is in your buffer array is a number? Are you calling any other methods/functions on ch?

Answer 3

Node's console.log() - the standard function for outputting - that I was using to print out the result behaves as printf and that is actually documented ( http://nodejs.org/docs/v0.4.11/api/stdio.html#console.log ). Silly me, thanks averyone for leding me to the solution.

sys.puts() prints the expected string.