There are two main ways to convert a string to a number in JavaScript. One way is to parse it and the other way is to change its type to a Number. All of the tricks in the other answers (e.g., …

None of the answers I see at the moment correctly convert -0 to "-0". Note that -0..toString() might appear to work, but it's working by converting 0 to "0", then applying the minus sign to it, …

To check if a variable (including a string) is a number, check if it is not a number: This works regardless of whether the variable content is a string or number.

Below is a very irritating example of how JavaScript can get you into trouble: If you just try to use parseInt() to convert to number and then add another number to the result it will concatenate …

Aug 20, 2009 · Does anyone know how can I check whether a variable is a number or a string in JavaScript?

20 This question already has answers here: How can I convert a string to an integer in JavaScript? (32 answers)

Mar 23, 2016 · Yes it gets a boolean from the < result and coerces it to string, but by then it's too late to affect how the comparison worked. JS < operator behavior depends on its two …

Here's another interesting, readable way to check if a string contains only digits. This method works by splitting the string into an array using the spread operator, and then uses the every() …

Apr 9, 2012 · } When you initialize an array with a number, it creates an array with the length set to that value so that the array appears to contain that many undefined elements. Though some …

Number formatting varies between cultures. Unless you're doing string comparison on the output, 1 the polite thing to do is pick undefined and let the visitor's browser use the formatting they're …