Javascript check if string is number

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Javascript check if string is number

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I'm hoping there's something in the same conceptual space as the old VB6 IsNumeric function? Of course, you can negate this if you need to.

For example, to implement the IsNumeric example you gave:. Only works if the string only contains numeric characters, else it returns NaN.

Empty strings may be a little counter-intuitive. If you're just trying to check if a string is a whole number no decimal placesregex is a good way to go. Other methods such as isNaN are too complicated for something so simple. Note that! The problem with parseFloat is that it will return a number if the string contains any number, even if the string doesn't contain only and exactly a number:.

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The problem with Number is that it will return a number in cases where the passed value is not a number at all! The problem with rolling your own regex is that unless you create the exact regex for matching a floating point number as Javascript recognizes it you are going to miss cases or recognize cases where you shouldn't.

And even if you can roll your own regex, why? There are simpler built-in ways to do it. However, it turns out that Number and isNaN does the right thing for every case where parseFloat returns a number when it shouldn't, and vice versa. So to find out if a string is really exactly and only a number, call both functions and see if they both return true:.

The accepted answer for this question has quite a few flaws as highlighted by couple of other users. Try the isNan function :. This function is different from the Number specific Number. However, even this one is far from complete. Leading zeros are not handled here, but they do screw the length test.

I have tested and Michael's solution is best. Vote for his answer above search this page for "If you really want to make sure that a string" to find it.The Number. It returns true if the passed value is an integer, otherwise it return false. Parameters: This function accepts a single parameter value which specifies the number which the user wants to check for integer. Return Value: The number. It will return true if the passed value is of the type Number and an integer, else it returns false.

Passing a number consisting of decimal places as an argument : If a decimal number is passed as argument, the function will return false. Passing a string as an argument : If the argument passed to the Number. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below. Writing code in comment?

Please use ide. JavaScript Math. Index inside map Function How to pass an array as a function parameter in JavaScript? How to check whether an array is subset of another array using JavaScript? File uploading in React. How to iterate over a JavaScript object? How to move mouse pointer to a specific position using JavaScript?

javascript check if string is number

How to clone array in ES6? How to get client IP address using JavaScript? Syntax: Number. How to call a function that return another function in JavaScript? Shubrodeep Banerjee. Check out this Author's contributed articles. Load Comments.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time.

Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Perhaps a regexp is what I need? Any tips? If you want to even support for float values Dot separated values then you can use this expression :. This method works by splitting the string into an array using the spread operatorand then uses the every method to test whether all elements characters in the array are included in the string of digits '' :.

Learn more. Check if string contains only digits Ask Question. Asked 10 years, 4 months ago. Active 8 months ago. Viewed k times. I want to check if a string contains only digits.

Alexander Abakumov 8, 6 6 gold badges 57 57 silver badges 93 93 bronze badges. Active Oldest Votes. Scott Evernden Scott Evernden This is great! Jason S Jason S k gold badges silver badges bronze badges.

FWIW, in when this answer was posted, it was not yet considered a bad practice. Several jQuery competitors that existed then, before jQuery had yet to win out, all practiced prototype extensions. Adithya Sai Adithya Sai 1, 1 1 gold badge 11 11 silver badges 26 26 bronze badges.

Lucke, the regex you suggested will only be able to find numbers with a decimal or higher than 9. Saranga Jayaruwan Saranga Jayaruwan 71 1 1 silver badge 3 3 bronze badges.

Here's another interesting, readable way to check if a string contains only digits. Grant Miller Grant Miller 12k 13 13 gold badges 61 61 silver badges 90 90 bronze badges. SC SC 4 4 silver badges 13 13 bronze badges.

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Linked Related Hot Network Questions.The Number. It returns true if the passed value is an integer, otherwise it return false. Parameters: This function accepts a single parameter value which specifies the number which the user wants to check for integer.

Return Value: The number. It will return true if the passed value is of the type Number and an integer, else it returns false. Passing a number consisting of decimal places as an argument : If a decimal number is passed as argument, the function will return false.

Passing a string as an argument : If the argument passed to the Number. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below. Writing code in comment?

Please use ide. JavaScript Math. How to pass an array as a function parameter in JavaScript? How to change the value of a global variable inside of a function using JavaScript? Multidimensional array in JavaScript File uploading in React. How to move mouse pointer to a specific position using JavaScript?

How to iterate over a JavaScript object? How to remove spaces from a string using JavaScript? Syntax: Number. Recommended Posts: How to call a function that return another function in JavaScript? How to override a JavaScript function? Shubrodeep Banerjee.

javascript check if string is number

Check out this Author's contributed articles. Load Comments.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Is there a command, like IsNumeric or something else, that can identify if a string is a valid number? This will return true if input is all numbers.

Don't know if it's any better than TryParsebut it will work. It will return true for all Numeric Digits not float and false if input string is any sort of alphanumeric. Please note : stringTest should not be an empty string as this would pass the test of being numeric. From Benchmarking IsNumeric Options. The TryParse method will try to convert the string to a number integer and if it succeeds it will return true and place the corresponding number in myInt.

If it can't, it returns false. Solutions using the int.

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Parse someString alternative shown in other responses works, but it is much slower because throwing exceptions is very expensive. Now you do: you should therefore avoid the Parse alternative. If you want to accept decimal numbers, the decimal class also has a.

JavaScript | Number.isInteger( ) function

Replace int with decimal in the above discussion, and the same principles apply. You can always use the built in TryParse methods for many datatypes to see if the string in question will pass.

In case you don't want to use int.

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Parse or double. Parse, you can roll your own with something like this:. I know this is an old thread, but none of the answers really did it for me - either inefficient, or not encapsulated for easy reuse.

I also wanted to ensure it returned false if the string was empty or null. TryParse returns true in this case an empty string does not cause an error when parsing as a number. So, here's my string extension method:. Or, if you want to test other types of number, you can specify the 'style'. So, to convert a number with an Exponent, you could use:. It is limited by not being able to convert strings that are too big to be contained in a double, but that is a limited requirement and I think if you are working with numbers larger than this, then you'll probably need additional specialised number handling functions anyway.

Keep in mind that just because a value is numeric doesn't mean it can be converted to a numeric type. For example, " NET numeric type not one defined in the standard library, that is.

If you want to check if a string is a number I'm assuming it's a string since if it's a number, duh, you know it's one.The Number. The source for this interactive example is stored in a GitHub repository. A Boolean indicating whether or not the given value is an integer. If the target value is an integer, return trueotherwise return false. If the value is NaN or Infinityreturn false. The compatibility table in this page is generated from structured data.

Get the latest and greatest from MDN delivered straight to your inbox. Sign in to enjoy the benefits of an MDN account. Last modified: Jan 15,by MDN contributors. Related Topics. Standard built-in objects Number Properties Number. NaN Number. Learn the best of web development Get the latest and greatest from MDN delivered straight to your inbox.

The newsletter is offered in English only at the moment. Sign up now. Sign in with Github Sign in with Google. Chrome Full support Edge Full support Firefox Full support IE No support No. Opera Full support Safari Full support 9.

Chrome Android Full support Firefox Android Full support Opera Android Full support Safari iOS Full support 9. Samsung Internet Android Full support 2.The isNaN function determines whether a value is NaN or not. Hence, the necessity of an isNaN function. NaN values are generated when arithmetic operations result in undefined or unrepresentable values.

Such values do not necessarily represent overflow conditions. A NaN also results from attempted coercion to numeric values of non-numeric values for which no primitive numeric value is available.

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For example, dividing zero by zero results in a NaN — but dividing other numbers by zero does not. Since the very earliest versions of the isNaN function specification, its behavior for non-numeric arguments has been confusing.

When the argument to the isNaN function is not of type Numberthe value is first coerced to a Number. The resulting value is then tested to determine whether it is NaN. Thus for non-numbers that when coerced to numeric type result in a valid non-NaN numeric value notably the empty string and boolean primitives, which when coerced give numeric values zero or onethe "false" returned value may be unexpected; the empty string, for example, is surely "not a number.

The function should be interpreted as answering the question, "is this value, when coerced to a numeric value, an IEEE 'Not A Number' value?

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Even with Number. Alternatively, in the absence of Number. There is a more usage oriented way to think of isNaN : If isNaN x returns falseyou can use x in an arithmetic expression not making the expression return NaN.

javascript check if string is number

If it returns truex will make every arithmetic expression return NaN. You can use this, for example, to test whether an argument to a function is arithmetically processable usable "like" a numberor if it's not and you have to provide a default value or something else. This way you can have a function that makes use of the full versatility JavaScript provides by implicitly converting values depending on context. Get the latest and greatest from MDN delivered straight to your inbox.

Sign in to enjoy the benefits of an MDN account. The compatibility table on this page is generated from structured data. Last modified: Jan 15,by MDN contributors. Related Topics. Collator Intl. DateTimeFormat Intl. DisplayNames Intl. ListFormat Intl. Locale Intl. NumberFormat Intl. PluralRules Intl. Learn the best of web development Get the latest and greatest from MDN delivered straight to your inbox.

The newsletter is offered in English only at the moment. Sign up now. Sign in with Github Sign in with Google. Chrome Full support 1.

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