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Message-ID: <1543388.qVoOGUtdWV@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Fri, 14 Oct 2011 20:54:16 +0200
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Subject: Re: FAQ Topic - How do I trim whitespace? (2011-10-14)
Newsgroups: comp.lang.javascript
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J.R. wrote:

> FAQ server wrote:
>> -----------------------------------------------------------------------
>> FAQ Topic - How do I trim whitespace?
>> -----------------------------------------------------------------------
>>
>> ECMAScript 5 defines `String.prototype.trim`. Where not supported,
>> it can be added as a function that uses a regular expression:
>>
>> if(!String.prototype.trim) {
>> String.prototype.trim = function() {
>> return String(this).replace(/^\s+|\s+$/g, "");
>> };
>> }
> 
>> The complete comp.lang.javascript FAQ is at
>> http://jibbering.com/faq/
>>
> 
> A few months ago, there was an article at Jibbering,com with a different
> version of this code:
> 
>    /** @see http://jibbering.com/faq/#trimString */
>    if (typeof String.prototype.trim !== "function") {
>      String.prototype.trim = function () {
>        // return String(this).replace(/^\s+|\s+$/g, "");
>        return this.replace(/^\s+|\s+$/g, "");
>      };
>    }
> 
> I think that is more consistent with ECMA-262 5th ed., 15.5.4.20.

`!x' requires

  RETURN Not(ToBoolean(GetValue(x)));

`typeof x !== y' requires
 
  lref := FUNCTION(x) {
    val := GetValue(x);
    IF Type(val) = Reference
    {
      IF IsUnresolvableReference(v)
      {
        RETURN "undefined";
      }
      val := GetValue(val);
    }
    RETURN GetResultByType(Type(val));
  }(x);
  lval := GetValue(lref);
  rref := Evaluate(y);
  rval := GetValue(rref);
  r := (rval === lval);  /* 11.9.6 */
  RETURN Not(r);

Implicit type conversion may suffice, especially iff it is more efficient 
than `typeof' (benchmarks anyone?); it is not logical to assume that the 
property would be assigned a non-function true-value, or a host object 
reference.

Regardless, strict comparison is pointless here.  `typeof' is not going to 
result in a non-string.

Also, we are at ES 5.1 (2011-06) by now, and section 15.5.4.20 says 
basically what the line does that is commented out here (there are 
implementations that do not implement whitespace as specified in ECMAScript, 
but it appears prudent that whitespace be handled either implementation-
independent or implementation-dependent in all places in a script library).


PointedEars
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