Le 27 août 2013 à 01:23, Brendan Eich <[email protected]> a écrit :
> Andrea Giammarchi wrote:
>> Is it very useful because you wrote for instead of while ?
>>
>> ```javascript
>> while (m = re.exec(str))
>> console.log(m[0])
>> ;
>> ```
>
> It is, for two reasons:
>
> 1. in JS only for can have a let or var binding in the head.
>
> 2. the utility extends to all for-of variations: array comprehensions,
> generator expresisons.
>
> /be
There is a third reason. The syntax:
```javascript
for (let m of re.execAll(str) {
// ...
}
```
has the clear advantage to express the intention of the programmer, and
*nothing more*. It does not require good knowledge of the details of the
language to understand what happens.
Indeed, when I read `while(m = re.exec(str))`, I really have to analyse the
following *additional* points:
* `=` is not a typo for `==` (here, some annotation would be useful);
* `RegExp#exec` returns a falsy value if *and only if* there is no more match;
* `re` has its global flag set, and its `.lastIndex` property has not been
disturbed.
All these tricks are unrelated to the intention of the programmer, and are just
distracting points, especially for any reader that use only occasionally
`RegExp#exec` with the global flag set.
In summary, citing [1]: "Don’t be clever, don’t make me think."
—Claude
[1] http://www.2ality.com/2013/07/meta-style-guide.html
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