Regex to replace multiple spaces with a single space

Regex to replace multiple spaces with a single space

Given a string like:
“The dog has a long tail, and it is RED!”
What kind of jQuery or JavaScript magic can be used to keep spaces to only one space max?
Goal:
“The dog has a long tail, and it is RED!”

Solutions/Answers:

Solution 1:

Given that you also want to cover tabs, newlines, etc, just replace \s\s+ with ' ':

string = string.replace(/\s\s+/g, ' ');

If you really want to cover only spaces (and thus not tabs, newlines, etc), do so:

string = string.replace(/  +/g, ' ');

Solution 2:

Since you seem to be interested in performance, I profiled these with firebug. Here are the results I got:

str.replace( /  +/g, ' ' )       ->  380ms
str.replace( /\s\s+/g, ' ' )     ->  390ms
str.replace( / {2,}/g, ' ' )     ->  470ms
str.replace( / +/g, ' ' )        ->  790ms
str.replace( / +(?= )/g, ' ')    -> 3250ms

This is on Firefox, running 100k string replacements.

I encourage you to do your own profiling tests with firebug, if you think performance is an issue. Humans are notoriously bad at predicting where the bottlenecks in their programs lie.

(Also, note that IE 8’s developer toolbar also has a profiler built in — it might be worth checking what the performance is like in IE.)

Solution 3:

var str = "The      dog        has a long tail,      and it is RED!";
str = str.replace(/ {2,}/g,' ');

EDIT:
If you wish to replace all kind of whitespace characters the most efficient way would be like that:

str = str.replace(/\s{2,}/g,' ');

Solution 4:

This is one solution, though it will target all space characters:

"The      dog        has a long tail,      and it is RED!".replace(/\s\s+/g, ' ')

"The dog has a long tail, and it is RED!"

Edit: This is probably better since it targets a space followed by 1 or more spaces:

"The      dog        has a long tail,      and it is RED!".replace(/  +/g, ' ')

"The dog has a long tail, and it is RED!"

Alternative method:

"The      dog        has a long tail,      and it is RED!".replace(/ {2,}/g, ' ')
"The dog has a long tail, and it is RED!"

I didn’t use /\s+/ by itself since that replaces spaces that span 1 character multiple times and might be less efficient since it targets more than necessary.

I didn’t deeply test any of these so lmk if there are bugs.

Also, if you’re going to do string replacement remember to re-assign the variable/property to its own replacement, eg:

var string = 'foo'
string = string.replace('foo', '')

Using jQuery.prototype.text:

var el = $('span:eq(0)');
el.text( el.text().replace(/\d+/, '') )

Solution 5:

I have this method, I call it the Derp method for lack of a better name.

while (str.indexOf("  ") !== -1) {
    str = str.replace(/  /g, " ");
}

Running it in JSPerf gives some surprising results.

Solution 6:

A more robust method: This takes care of also removing the initial and trailing spaces, if they exist. Eg:

// NOTE the possible initial and trailing spaces
var str = "  The dog      has a long   tail, and it     is RED!  "

str = str.replace(/^\s+|\s+$|\s+(?=\s)/g, "");

// str -> "The dog has a long tail, and it is RED !"

Your example didn’t have those spaces but they are a very common scenario too, and the accepted answer was only trimming those into single spaces, like: ” The … RED! “, which is not what you will typically need.