find whether first letter of a string is capital or not

Question

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Check if first letter of word is a capital letter

I want to write a function in which I pass string as argument. Then I want to find out whether the first letter of this string is capital or not. If it is capital then return true otherwise return false. How can I achieve this in javascript? Any simple demo, I will later modify according to my need.

Are you asking to check if the first *character* is a letter and is capital, or if merely the first letter of the string is capital? Those are two different things. Given your question, the following string should return true `"...123Abc"` — I Hate Lazy, Dec 06 '12 at 13:09

Cerbrus · Answer 1 · 2012-12-06T13:21:40.840

4

var myString = "Whatever you want to test"
console.log(myString[0] == myString[0].toUpperCase());
//Returns true

myString = "whatever you want to test"
console.log(myString[0] == myString[0].toUpperCase());
//Returns false

myString[0] doesn't work in (Somewhere around) IE7/IE8 and lower, use myString.charAt(0) if you need the script to be compatible with those browsers.

edited Dec 06 '12 at 13:21

answered Dec 06 '12 at 12:59

Cerbrus

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The "array syntax" for strings don't works on IE7 and less. Am i right ? – Magus Dec 06 '12 at 13:02
Might be, I'll modify accordingly. Edit: Yup, that's right. – Cerbrus Dec 06 '12 at 13:02
IE 8 and lower have that issue. – I Hate Lazy Dec 06 '12 at 13:04
@IHateLazy: All pages I find on it mention IE7 and lower. – Cerbrus Dec 06 '12 at 13:09
According to [this MSDN page](http://msdn.microsoft.com/en-us/library/ie/ecczf11c%28v=vs.94%29.aspx): *"You can access an individual character of a string as a read-only array-indexed property. This feature was introduced in Internet Explorer 9 standards mode..."* – I Hate Lazy Dec 06 '12 at 13:14
@IHateLazy: Hm, Editing... Damn you, Microsoft. – Cerbrus Dec 06 '12 at 13:21
wait, I just fired up VirtualBox, and it seems to work in IE8. Strange that the docs would suggest otherewise. – I Hate Lazy Dec 06 '12 at 13:23
@IHateLazy: There, this should cover it. – Cerbrus Dec 06 '12 at 13:24

piatek · Accepted Answer · 2012-12-06T20:09:08.923

4

You can use String.charCodeAt(). This function returns a a unicode value of the character. Uppercase letters have a different value than lowercase ones.

Check the docs: http://dochub.io/#javascript/string.charcodeat

function isFirstLetterCapital(string) {
  return string.charCodeAt(0) === string.toUpperCase().charCodeAt(0);
}

Edit:

charAt is actually faster - http://jsperf.com/string-operations-order. Thanks Cerbrus for pointing this out.

function isFirstLetterCapital(string) {
  return string.charAt(0) === string.charAt(0).toUpperCase();
}

edited Dec 06 '12 at 20:09

answered Dec 06 '12 at 13:01

piatek

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Use `string.charAt(0).toUpperCase();`, [that's lighter](http://jsperf.com/string-operations-order). Also, why `charCodeAt` instead of `charAt`? – Cerbrus Dec 06 '12 at 13:10
1

but you can't uppercase a unicode value ;) – piatek Dec 06 '12 at 13:12
great stuff. charCodeAt was just the first thing that came to my mind. – piatek Dec 06 '12 at 20:09

score 3 · Answer 3 · answered Dec 06 '12 at 13:01

3

if(yourString.match(/^[A-Z]/)) ...

answered Dec 06 '12 at 13:01

Samuel Caillerie

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score 1 · Answer 4 · answered Dec 06 '12 at 13:00

1

function isFirstLetterUpperCase(string) {
   var firstLetter = string.charAt(0);
   return firstLetter == firstLetter.toUpperCase();
}

answered Dec 06 '12 at 13:00

Magus

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find whether first letter of a string is capital or not

4 Answers4