A minor problem with the basic regular expression

Question

A minor problem with the basic regular expression

As a JavaScript novice, I recently delved into the world of regular expressions for the first time.

After attempting to perform some matching operations, I found myself puzzled by the results.

My goal was simple: I wanted to match every website name in the following sentence:

"I go to google.com to search, to facebook.com to share and to yahoo.com to send an email."

This is the code I used:

var text = "I go to google.com to search, to facebook.com to share and to yahoo.com to send an email.";
var pattern = /\w+\.\w+/g;

var matches = pattern.exec(text);

document.write("matches index : " + matches.index + "<br>");
document.write("matches input : " + matches.input + "<br>");
document.write("<br>");
for(i=0 ; i<matches.length ; i++){
    document.write("match number " + i + " : " + matches[i] + "<br>");
}

Here's what I got as a result:

matches index : 0

matches input : i go to google.com to search, to facebook.com to share and to yahoo.com to send an email

match number 0 : google.com

I wondered why it only matched 'google.com' and not the other websites. Can anyone explain?

javascript regex

Answer 1

Answer №1

Quoting the information provided in the MDN documentation:

If your regular expression has the "g" flag enabled, you can make use of the exec method repeatedly to find consecutive matches within the same string. In such cases, the search initiates at the substring of str indicated by the regular expression's lastIndex property (test will similarly progress the lastIndex property).

Hence, execute it multiple times like this:

var match, i = 0;
while(match = pattern.exec(text)) {
    document.write("match number " + (i++) + " : " + match[0] + "<br>");
}

Alternatively, if there are no capture groups, utilize .match():

var matches = text.match(pattern);
for(i=0 ; i<matches.length ; i++){
    document.write("match number " + i + " : " + matches[i] + "<br>");
}

Answer 2

Quoting the information provided in the MDN documentation:

If your regular expression has the "g" flag enabled, you can make use of the exec method repeatedly to find consecutive matches within the same string. In such cases, the search initiates at the substring of str indicated by the regular expression's lastIndex property (test will similarly progress the lastIndex property).

Hence, execute it multiple times like this:

var match, i = 0;
while(match = pattern.exec(text)) {
    document.write("match number " + (i++) + " : " + match[0] + "<br>");
}

Alternatively, if there are no capture groups, utilize .match():

var matches = text.match(pattern);
for(i=0 ; i<matches.length ; i++){
    document.write("match number " + i + " : " + matches[i] + "<br>");
}

Answer 3

Answer №2

One interesting alternative to iterating through a string is using the replace method, even if no actual replacements are needed.

Consider implementing it like this:

var items = text.replace(pattern,function($0){console.log($0);});

Check out the live demonstration here

Answer 4

One interesting alternative to iterating through a string is using the replace method, even if no actual replacements are needed.

Consider implementing it like this:

var items = text.replace(pattern,function($0){console.log($0);});

Check out the live demonstration here

A minor problem with the basic regular expression

Answer №1

Answer №2

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