How to Check If a String Only Contains Letters

Check if string contains only letters in javascript

With /^[a-zA-Z]/ you only check the first character:

^: Assert position at the beginning of the string
[a-zA-Z]: Match a single character present in the list below:
- a-z: A character in the range between "a" and "z"
- A-Z: A character in the range between "A" and "Z"

If you want to check if all characters are letters, use this instead:

/^[a-zA-Z]+$/.test(str);

^: Assert position at the beginning of the string
[a-zA-Z]: Match a single character present in the list below:
- +: Between one and unlimited times, as many as possible, giving back as needed (greedy)
- a-z: A character in the range between "a" and "z"
- A-Z: A character in the range between "A" and "Z"
$: Assert position at the end of the string (or before the line break at the end of the string, if any)

Or, using the case-insensitive flag i, you could simplify it to

/^[a-z]+$/i.test(str);

Or, since you only want to test, and not match, you could check for the opposite, and negate it:

!/[^a-z]/i.test(str);

How to check if a string only contains letters, numbers, underscores and period. Flutter/Dart

The problem with your RegExp is that you allow it to match substrings, and you match only a single character. You can force it to require that the entire string be matched with ^ and $, and you can match against one or more of the expression with +:

print(RegExp(r'^[a-z]+$').hasMatch(mainString));

To match all the characters you mentioned:

print(RegExp(r'^[A-Za-z0-9_.]+$').hasMatch(mainString));

Java String - See if a string contains only numbers and not letters

If you'll be processing the number as text, then change:

if (text.contains("[a-zA-Z]+") == false && text.length() > 2){

to:

if (text.matches("[0-9]+") && text.length() > 2) {

Instead of checking that the string doesn't contain alphabetic characters, check to be sure it contains only numerics.

If you actually want to use the numeric value, use Integer.parseInt() or Double.parseDouble() as others have explained below.

As a side note, it's generally considered bad practice to compare boolean values to true or false. Just use if (condition) or if (!condition).

JavaScript: check if a giving string contains only letters or digits

Add 0-9 also to your regex

 boolean onlyLetters(String str) {
   return str.match("^[A-Za-z0-9]+$");
 }

Checking if string is only letters and spaces

The function can be written more simpler and correctly if to use standard C functions isalpha and isblank declared in header <ctype.h> For example

#include <ctype.h>

//...

int checkString( const char s[] )
{
    unsigned char c;

    while ( ( c = *s ) && ( isalpha( c ) || isblank( c ) ) ) ++s;

    return *s == '\0'; 
}

If you want to check whether a string contains white spaces then instead of function isblank you should use function isspace.

Take into account that it is not a good idea to use statement continue in such simple loops. It is better to rewrite the loop without the continue statement.

And instead of function scanf it is better to use function fgets if you want to enter a sentence The function allows to enter several words as one string until the Enter will be pressed.

For example

fgets( str1, sizeof( str1 ), stdin );

Take into account that the function includes the new line character. So after entering a string you should remove this character. For example

size_t n = strlen( str1 );
if ( n != 0 && str1[n-1] == '\n' ) str1[n-1] = '\0';