if charAt equal to a list of characters

Question

I want something like the following in Javascript

if str.charAt(index) (is in the set of) {".", ",", "#", "$", ";", ":"}

Yes, I know this must be simple, but I can't seem to get the syntax right. What I have now is

theChar = str.charAt(i);
if ((theChar === '.') || (theChar === ',') || (theChar === ... )) {
  // do stuff
}

This works, but there must be a better way.

Edit: I did this, but not sure if it's GOOD or not:

var punc = {
    ".":true,
    ",":true,
    ";":true,
    ":":true
};

if (punc[str.charAt[index]) { ...

Steffi

Answer 1

Define an array with those chars and simply search in the array. One way to do that is the following:

var charsToSearch = [".", ",", "#", "$", ";", ":"];
var theChar = str.charAt(i); /* Wherever str and i comes from */

if (charsToSearch.indexOf(theChar) != -1) {
    /* Code here, the char has been found. */
}

Incursion

@L105 are you sure about that? – Phalange

Going to make a jsPerf. – Hy

While you're at it, make one using String.indexOf as well, e.g. ".,#$;:".indexOf(theChar) !== -1. Although I don't think performance will matter much for this snippet. – Chanson

In my test the String indexOf is fastest in Firefox, followed by the regex and then the array. It's the opposite in Chrome. – Phalange

In my test, regex is 59% slower in chrome. jsperf.com/regexndexof, second time : 9% slower. – Hy

All of these work, but I am actaully sticking with the solution I came up with for this instance just because I really like the syntax if (punc[str.charAt[index]) { ... } even though it's a bit wordy in creating the set in the first place. – Steffi

Answer 2

You can do it with a regular expression:

var theChar = str.charAt(i);
if (/[.,#$;:]/.test(theChar)) {
  // ...
}

Phalange

Not very friendly for new JavaScript programmers, but I guess it's good to demonstrate a practical solution. – Chanson

@MattiasBuelens I guess it depends on where the new JavaScript programmer comes from :) By the time I learned JavaScript, I'd known about regular expressions for a long time. – Phalange

ah, that's what I was trying to do, but ten I got distracted by sets. – Steffi