How do i distinguish between number string and character string?

Question

var snumber1 = "123456789";
var scharacter2 = "abcdefgh";

there're two strings. how do i make sure snumber1 contains only numbers?? What regex??

A regex isn't really necessary here, but if you're curious it would be `/^\d+$/` for only numbers, or `/^\d*$/` if you want to match the empty string also. — Ismail Badawi, Jul 18 '11 at 14:39

score 2 · Answer 1 · edited May 23 '17 at 12:13

2

The regex to determine if something is just numbers is this:

"^\d+$"  or  "^[0-9]+$"

Source: StackOverFlow 273141

edited May 23 '17 at 12:13

Community

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answered Jul 18 '11 at 14:39

JakeJ

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Bakudan · Accepted Answer · 2011-07-18T16:01:21.133

2

var snumber1 = "123456789";
//built-in function
alert ( !isNaN ( snumber1 ) );
//regexp
alert ( /^[0-9]+$/.test ( snumber1 ) );
//another regexp
alert ( /^\d+$/.test ( snumber1 ) );
//convert to Number object
alert ( parseFloat ( snumber1 ) === Number ( snumber1 ) );

edited Jul 18 '11 at 16:01

answered Jul 18 '11 at 14:44

Bakudan

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`/[0-9]/` will match any string that has at least one digit. – Ismail Badawi Jul 18 '11 at 14:52
what's the difference between !isNaN and isNaN?? Can isNaN be enough?? – DrStrangeLove Jul 18 '11 at 14:53
Yes, just ask to see if isNaN() is false. – Isaac Lubow Jul 18 '11 at 15:24
@isbadawi my bet - I fixed it. – Bakudan Jul 18 '11 at 16:01
@DrStrangeLove !isNaN is just to follow the logic of the example - if it`s a number will alert true, if not - false. – Bakudan Jul 18 '11 at 16:03

score 1 · Answer 3 · answered Jul 18 '11 at 14:35

1

You need this function:

isNaN(string)

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/isNaN

answered Jul 18 '11 at 14:35

Joe

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See the above link: `isNaN("12")` //returns false; `isNaN(12)` //returns false – Jiri Kriz Jul 18 '11 at 14:45
@isbadani: how does this help? – Jiri Kriz Jul 18 '11 at 14:58
@Jiri `isNaN` does (more or less) the opposite of what the OP wants (the OP needs "is not not a number"). – Ismail Badawi Jul 18 '11 at 15:10

James Sumners · Answer 4 · 2011-07-18T18:41:07.993

1

Regular expressions are unnecessary:

var snumber1 = "123456789",
    scharacter2 = "abcdefgh";

if ( isNaN(+snumber1) ) {
  alert('snumber is not a number!');
}

if ( !isNaN(+scharacter2) ) {
  alert('scharacter2 is not a string!');
}

Note that I am using the + operator to do type coercion. Doing so will always result in a number or NaN. If you use the parseInt or parseFloat functions you could get '10' from parseInt('010abc', 10). This clearly doesn't pass your test for "only numbers" (*).

edited Jul 18 '11 at 18:41

answered Jul 18 '11 at 14:45

James Sumners

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Better yet, considering isNaN has edge cases, use `if(+sNumber1 != +sNumber1)`, which is true iff sNumber1 is not a number. – Thaddee Tyl Jul 18 '11 at 16:04
@Thaddee: `+sNumber != +sNumber` has *exactly* the same edge cases as `isNaN` with an additional downside that it's quite a bit slower than `isNaN` - believe it or not, `isNaN` performs the same number conversion on the argument passed before checking it. This also means that the `+` in `isNaN(+str)` is completely unnecessary and just adds extra overhead with no benefit. – Andy E Sep 16 '11 at 08:12
1

@Andy E, I wasn't aware of that. Thank you. – James Sumners Sep 16 '11 at 12:39

score 1 · Answer 5 · edited Jan 30 '12 at 09:43

1

You should use SWITCH statements instead of IF.

var valueA=100

switch(/^[0-9]+$/.test( valueA ))
{
    case false:
        alert ("'" + valueA + "'" + " Is NOT a number.Try Again");
        break;
    case true;
        alert ("you've got numbers")
        break;
}

This will return true.

edited Jan 30 '12 at 09:43

Myrtle

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answered Jan 30 '12 at 01:32

CodeyKane

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score 0 · Answer 6 · answered Jul 18 '11 at 14:36

0

you could use parseInt

if (parseInt(snumber1) == snumber1){ alert('is a number'); }

answered Jul 18 '11 at 14:36

Mihai Iorga

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How do i distinguish between number string and character string?

6 Answers6