javascript - count spaces before first character of a string

Question

What is the best way to count how many spaces before the fist character of a string?

str0 = 'nospaces even with other spaces still bring back zero';
str1 = ' onespace do not care about other spaces';
str2 = '  twospaces';

Out of curiosity, why do you want to count the spaces? You know about trim right? — rybo111
– rybo111, Commented Sep 13, 2014 at 14:00
i have a text box for quick edit of json string and i need to know how many spaces before the string starts to figure out where it is in the object — K3NN3TH
– K3NN3TH, Commented Sep 13, 2014 at 14:01
You could use the regex /^\s+/ and count using str0.match(/^\s+/)[0].length — soktinpk
– soktinpk, Commented Sep 13, 2014 at 14:01
Try to use jQuery and add ltrim functions in combination with suggested solution below. A reference link: somacon.com/p355.php — Sanket Tarun Shah
– Sanket Tarun Shah, Commented Sep 13, 2014 at 14:03

folkol · Accepted Answer · 2014-09-13 14:15:56Z

66

Use String.prototype.search

'    foo'.search(/\S/);  // 4, index of first non whitespace char

EDIT: You can search for "Non whitespace characters, OR end of input" to avoid checking for -1.

'    '.search(/\S|$/)

edited Sep 13, 2014 at 14:15

answered Sep 13, 2014 at 14:06

folkol

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6 Comments

JAAulde Over a year ago

I like this. It does require that at least one non-whitespace char appears, but it's nice and clean. I suggest this addition: ' '.search(/\S|$/) which will account for strings which do not have a non-whitespace char.

folkol Over a year ago

Yeah, it will return -1 if there is no match for \S.

JAAulde Over a year ago

With or without my addition, depending on the OP's needs, I like this answer better than my own. Good thinking.

folkol Over a year ago

Yeah, that is a nice way to handle it. I'll update the answer.

K3NN3TH Over a year ago

there will be no case of all white space but still nice to know

|

JAAulde · Accepted Answer · 2014-09-13 14:03:54Z

10

Using the following regex:

/^\s*/

in String.prototype.match() will result in an array with a single item, the length of which will tell you how many whitespace chars there were at the start of the string.

pttrn = /^\s*/;

str0 = 'nospaces';
len0 = str0.match(pttrn)[0].length;

str1 = ' onespace do not care about other spaces';
len1 = str1.match(pttrn)[0].length;

str2 = '  twospaces';
len2 = str2.match(pttrn)[0].length;

Remember that this will also match tab chars, each of which will count as one.

answered Sep 13, 2014 at 14:03

JAAulde

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3 Comments

K3NN3TH Over a year ago

have to wait 6 min to answer

JAAulde Over a year ago

Take a look at my comment on @folkol's answer, and then accept that answer. I like that solution better. You can determine whether you need my addition or not depending upon your circumstances and needs, but overall it's cleaner.

K3NN3TH Over a year ago

ya, finding index was pretty slick indeed. I'll never look at a string the same.

danday74 · Accepted Answer · 2017-10-14 02:05:08Z

9

You could use trimLeft() as follows

myString.length - myString.trimLeft().length

Proof it works:

let myString = '       hello there '

let spacesAtStart = myString.length - myString.trimLeft().length

console.log(spacesAtStart)

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/TrimLeft

answered Oct 14, 2017 at 2:05

danday74

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1 Comment

Sergiu Over a year ago

If you need to support IE, trimLeft is not an option. Just use the regex solutions above. Otherwise, this is awesome.

iNikkz · Accepted Answer · 2014-09-13 14:24:21Z

5

str0 = 'nospaces';
str1 = ' onespace do not care about other spaces';
str2 = '  twospaces';

arr_str0 = str0.match(/^[\s]*/g);
count1 = arr_str0[0].length;
console.log(count1);

arr_str1 = str1.match(/^[\s]*/g);
count2 = arr_str1[0].length;
console.log(count2);

arr_str2 = str2.match(/^[\s]*/g);
count3 = arr_str2[0].length;
console.log(count3);

Here: I have used regular expression to count the number of spaces before the fist character of a string.

^ : start of string.
\s : for space
[ : beginning of character group
] : end of character group

answered Sep 13, 2014 at 14:24

iNikkz

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Comments

maowtm · Accepted Answer · 2014-09-13 14:10:11Z

0

str.match(/^\s*/)[0].length

str is the string.

answered Sep 13, 2014 at 14:10

maowtm

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Comments

David Cervera · Accepted Answer · 2023-03-30 07:37:25Z

0

A bit late, but just for giving a different answer

let myString     = "     string";
let count_spaces = myString.length - myString.trim().length;

Note that if the string has spaces at the end will also be added.

answered Mar 30, 2023 at 7:37

David Cervera

1

2 Comments

Andy A. Over a year ago

Good idea. But its explicit asked to count spaces at the beginning of the string. So why not use trimStart() instead of trim()?

David Cervera Over a year ago

Yes! you are right It can also be used, as also trimEnd() for other cases, ofc.

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