regex - Javascript, String formatting: I need the first 4 letters of a string, lowercase, whitespace skimmed, symbols removed -

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...I should just list them:

1. First 4 letters/numbers, with...
2. All lowercase.
3. Whitespace stripped.
4. Symbols removed.

Should be simple. What's the best way to do this?

...I should just list them:

1. First 4 letters/numbers, with...
2. All lowercase.
3. Whitespace stripped.
4. Symbols removed.

Should be simple. What's the best way to do this?

• javascript
• regex
• string
• formatting

Share Improve this question Follow asked Jul 10, 2010 at 9:26 HamsterHamster 57722 gold badges77 silver badges1313 bronze badges 2

• Have you given the correct order of these operations? For example, if you have "A B C D", if you follow your rules you get "ab". Somehow I think you might want "abcd" though. – Joseph Mansfield Commented Jul 10, 2010 at 9:34
• Ah, right. Yeah I need the whitespace and symbols stripped before pressing to 4 characters. Thanks. – Hamster Commented Jul 10, 2010 at 9:40

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3 Answers 3

Sorted by: Reset to default 5

1. slice(0, 4)
2. toLowerCase()
3. replace(/\s/g, '')
4. replace(/[^\w\s]/g, '')

The third and fourth regexes can be bined more simply as just \W, to remove all non-alphanumerics, if that's what you want. If the ‘symbols’ you want to remove are more specific than that, you'll have to put them in a character class explicitly, eg. /[!"#...]/g. If you only mean that you want to remove whitespace at the start and end of a string (“trimming”):

replace(/^\s+/, '').replace(/\s+$/, '')

instead.(*)

Chain them together in whatever order is appropriate. If you want to chop to four characters after you've removed unwanted characters:

var processed= str.replace(/\W/g, '').toLowerCase().slice(0, 4);

(*: string.trim() is also available in ECMAScript Fifth Edition but not all browsers support it yet. You can hack trim() support into String.prototype if you would like to using string.trim() on all browsers today:)

if (!('trim' in String.prototype)) {
    String.prototype.trim= function() {
        return (''+this).replace(/^\s+/, '').replace(/\s+$/, '');
    };
}

Something like this?

"  MY STRING  ".replace(/^\s+|\s+$/g, '').substring(0,4).toLowerCase()

You can remove desired symbols with similar replace-method.

Whitespace stripped.

only from the ends, or the whole string? The following strips all whitespace (and anything other than numbers and letters - \w includes underscores too) from the string.

str = str.replace(/[^a-z0-9]+/ig).substring(0, 4).toLowerCase();

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