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Jenuel Oras Ganawed
Jenuel Oras Ganawed

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Check String If its a number

#javascript #webdev #programming #shortread

When checking string if its a number, there are a lot of ways you can check a string if its a number. You can use regex, isNaN() function, or a plus operator, or parseInt.

But the best function that we can use is a function called Number().

The Number() function converts the argument to a number representing the object’s value. If it fails to convert the value to a number, it returns NaN.

We can use it with strings also to check whether a given string is a number or not.

console.log(Number('195')) // 195
console.log(Number('boo')) // Nan
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Oldest comments (7)

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yigitt profile image
yigitt •

how plus operator is used for conversion? afaik it combines strings.

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brojenuel profile image
Jenuel Oras Ganawed • • Edited

The + operator returns the numeric value of the string, or NaN, if the string isn’t purely numeric characters.

example:

console.log(+'195'); // 195
console.log(+'boo'); // NaN
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yigitt profile image
yigitt •

Is there Any difference with other methods? ParseInt() and Number().

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brojenuel profile image
Jenuel Oras Ganawed • • Edited

parseInt() is used for parsing a string to number.. It has similarities with Number() but parseInt() will extract a string to int. Number() on the other hand it converts string to number, and support different number format.

//example
let str = '34e10';

console.log(Number(str)); // 340000000000

console.log(parseInt(str)); // 34
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yigitt profile image
yigitt •

Thank you Jenuel. Nice post.

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brojenuel profile image
Jenuel Oras Ganawed •

thanks mate, :) happy to help :)

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darkwiiplayer profile image
𒎏Wii 🏳️‍⚧️ •

Number is cool, but it doesn't tell you whether something is a number. Au contraire: it will turn anything into a number, so tpeof Number(something) will always be "number" regardless of what something was before.

The easiest way to find out if a string is a number is to simply call isNaN on it and negate the output.

const isNumber = value => !isNaN(value)
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