Checking the number inside a string in javascript

Question

I have a string, say

var Str = 'My name is 123 and my name is 234'.

Now I split this as

var arrStr = Str.split(' ');

I iterate through the array and have different logic depending upon whether the word is a string or number. How do i check that? I tried typeof which didn't work for me.

EDIT:

After Seeing multiple answers. Now, I am in despair, which is the most efficient way?

score 6 · Accepted Answer · edited May 23 '17 at 12:05

6

If you care only about the numbers, then instead of using split you can use a regular expression like this:

var input = "My name is 123 and my name is 234";
var results = input.match(/\d+/g)

If you care about all pieces, then you can use another expression to find all non-space characters like this:

var input = "My name is 123 and my name is 234";
var results = input.match(/\S+/g)

Then iterate them one by one, and check if a given string is a number or not using the famous isNumeric() function posted by @CMS in this famous question.

function isNumber(n) {
    return !isNaN(parseFloat(n)) && isFinite(n);
}

NOTE: Thanks to @Pointy and if you want them as numbers, input.match(/\d+/g).map(Number).

edited May 23 '17 at 12:05

Community

1
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answered Oct 29 '13 at 14:34

Ibrahim Najjar

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1

... and if you want them as numbers, `input.match(/\d+/g).map(Number)` – Pointy Oct 29 '13 at 14:35
1

Gotta love how 4 people upvoted this before you corrected it. Prior to your edit the result of this was simpy `["d"]`. Good job on catching that yourself though. – James Donnelly Oct 29 '13 at 14:36
@JamesDonnelly Yeah I noticed that, sometimes they just like the sound of it :) – Ibrahim Najjar Oct 29 '13 at 14:37
@Sniffer : Some suggest unary + is faster than parseFloat() ? – cipher Oct 29 '13 at 14:57
@cipher Have you seen a benchmark about this, and by how much ? How much do you care for speed here. Anyway the `isNumberic()` method is taken from a famous question with a lot of discussions and opinions and the guys seem to be happy with it :). – Ibrahim Najjar Oct 29 '13 at 14:59
If i can get to same solution using different methods. It's just: "why not the fastest ?". But since the question was discussed for long. Maybe there's a reason. Anyways, thanks – cipher Oct 29 '13 at 15:05
@cipher You are correct, but that's a very well written and professional answer written bythe best, so don't hesitate :). Please don't forget to accept this answer if it solves your problem. – Ibrahim Najjar Oct 29 '13 at 15:07

James Donnelly · Answer 2 · 2013-10-29T14:44:52.737

2

You need to attempt to convert your array values to an integer.

To iterate them you can use a for loop:

for(i=0;i<arrStr.length;i++) {
    var result = !isNaN(+arrStr[i]) ? 'number' : 'string';
    console.log(result);
}

Here I'm using a unary + to attempt to convert the value of each array value to a number. If this fails, the result will be NaN. I'm then using JavaScript's isNaN() method to test if this value is NaN. If it isn't, then it's a number, otherwise it's a string.

The result of this using the string you've provided is:

string
string
string
number
string
string
string
string
number

To use this in an if statement, we can simply:

for(i=0;i<arrStr.length;i++) {
    if(isNaN(+arrStr[i])) {
        /* Process as a string... */
    }
    else {
        /* Process as a number... */
    }
}

JSFiddle demo.

edited Oct 29 '13 at 14:44

answered Oct 29 '13 at 14:38

James Donnelly

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I think the unary + does evil? `typeof +"string"` returns number – cipher Oct 29 '13 at 14:44
@cipher I fixed my answer, sorry about that! – James Donnelly Oct 29 '13 at 14:45
I'm seeing you basically replaced `Number(arrStr[i])` to `+arrStr[i]` , Am I Correct? – cipher Oct 29 '13 at 14:48
1

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#-_.28Unary_Plus.29 – James Donnelly Oct 29 '13 at 14:54

score 1 · Answer 3 · answered Oct 29 '13 at 14:39

To expound on Sniffer's answer...

var input = "My name is 123 and my name is 234";
var numberArray = input.match(/\d+/g);
var wordArray = input.match(/[A-Za-z]+/g);

for (var number in numberArray)
{
    //do something
}
for (var word in wordArray)
{
    //do something
}

cipher · Answer 4 · 2013-10-29T14:52:13.100

While researching, I found out about the Number() object. This is generally used to work with manipulation of numbers. MDN has a good documentation .

I found out that Number() returns NaN (Not a Number) when not passed a number. Since no number returns NaN, It could be a good way to check whether the passed object is string or a number literal.

So my code would be:

if (Number(arrStr[i]) == NaN){
    //string
} else  {
    //number
}

Checking the number inside a string in javascript

4 Answers4