Best Way to Implement isNumber() in JavaScript

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#1

How can I write an isNumber() function in JavaScript?

I’ve come across this answer:

function isNumber(val) { return val === +val; }

Is there a better way to implement this? Specifically, I’m looking for a solution related to javascript isNumber.

#2

Using typeof Operator: In my experience, a reliable way to check for numbers in JavaScript is using the typeof operator combined with a check for NaN. This helps identify actual number values and exclude NaN:

function isNumber(val) {
    return typeof val === 'number' && !isNaN(val);
}

This approach ensures the function explicitly checks for the ‘number’ type and rules out NaN. It’s a straightforward and effective solution to tackle the javascript isNumber check.

#3

Another approach, which I’ve found to be quite elegant, involves using Number.isFinite(). This built-in method is designed to ensure that the value is a finite number:

function isNumber(val) {
    return Number.isFinite(val);
}

What’s great about this solution is its simplicity and directness. It precisely handles the validation of a finite number while avoiding pitfalls with other types, giving a clean result for the javascript isNumber check.

#4

In some cases, especially when dealing with strings that represent numbers, it might be useful to leverage a regular expression. From my experience, this approach can expand the validation to include numeric strings:

function isNumber(val) {
    return typeof val === 'string' ? /^-?\d+(\.\d+)?$/.test(val) : typeof val === 'number' && !isNaN(val);
}

This method is versatile since it checks if the input is a string that fits a numeric pattern or if it’s an actual number. This way, you cover more ground for various input types in your javascript isNumber validation.