can i replace regExp with another regExp?

Question

 var str='The_Andy_Griffith_Show'; // string to perform replace on
 var regExp1=/\s|[A-Z]/g;
 var regExp2=/[^A-Z]/g;            // regular expression
 var str2 =str.replace(regExp2,regExp1); 
 // expected output: The_ Andy_ Griffith_ Show

I want to replace all the first capital letters of a string with a space and that same letter, and if that's not possible is there a workaround?

Per developer.mozilla.org/en/docs/Web/JavaScript/Reference/… no. You can use either string or function - RegExp is an object — eithed
– eithed, Commented Jun 9, 2017 at 8:09

Wiktor Stribiżew · Accepted Answer · 2017-06-09 08:11:49Z

1

If you want to add a space before any captial letter, it is enough to use

var str='The_Andy_Griffith_Show';
str = str.replace(/[A-Z]/g, ' $&')
console.log(str); // => "  The_ Andy_ Griffith_ Show"

Here, /[A-Z]/g matches all ASCII uppercase letters and $& is a backreference to the whole match value.

If you want to only add a space before the first capital letter in a word, you need to use capturing groups and backreferences to thier values in the replacement pattern:

var str='The_Andy_Griffith_Show'; // string to perform replace on
str = str.replace(/(^|[^A-Z])([A-Z])/g, '$1 $2')
console.log(str); // => "  The_ Andy_ Griffith_ Show"

Remove ^| if you do not want to add space before a capital letter at the string start (i.e. use /([^A-Z])([A-Z])/g).

answered Jun 9, 2017 at 8:11

Wiktor Stribiżew

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LukStorms · Accepted Answer · 2017-06-09 08:37:59Z

0

Just an alternative to the other answers.
To get that expected result you could just match the non-uppercases that are followed by an uppercase character, then replace them with the match $& and a space.

For example:

var str='The_Andy_Griffith_Show';
str = str.replace(/[^A-Z](?=[A-Z])/g, '$& ')
console.log(str);

Or simply match those uppercases followed by an uppercase character.

var str='The_Andy_Griffith_Show';
str = str.replace(/[_](?=[A-Z])/g, '$& ')
console.log(str);

answered Jun 9, 2017 at 8:37

LukStorms

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Yosvel Quintero · Accepted Answer · 2017-06-10 08:58:43Z

0

To add space to all occurrences of capital letters:

var str = 'The_Andy_Griffith_Show',
    str2 = str.replace(/[A-Z]/g, letter => ` ${letter}`);
    
console.log(str2);

Notice that if you want no to add space to the first letter occurrence, just use the regular expression /(?!^)[A-Z]/g.

edited Jun 10, 2017 at 8:58

answered Jun 9, 2017 at 8:12

Yosvel Quintero

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