confusing error for fs.createReadStream(path, { start: "90", end: "99"})

[coolaj86]

This concerns the case that a string is passed in to createReadStream start or end, instead of a number.

There are several places in fs.js where this.pos += {{whatever}} will result in string concatenation and throw a confusing error:

  binding.read(fd, buffer, offset, length, position, wrapper);
          ^
Error: Length extends beyond buffer

I propose that this.pos = parseInt(this.start, 10) be used (in the if block around line 1040 in fs.js) instead of this.pos = this.start.

I'll be happy to submit the pull request if you like.

In context:

if (this.start !== undefined) {
  if (this.end === undefined) {
    this.end = Infinity;
  }      

  if (this.start > this.end) {
    throw new Error('start must be <= end');
  }      

  this.pos = parseInt(this.start, 10);
}   

...

[bnoordhuis]

I'll take a patch but don't be accommodating, just throw a TypeError when start or end isn't a number.