Question

Is there a way to convert NaN values to 0 without an if statement? Example:

if (isNaN(a)) a = 0;

It is very annoying to check my variables every time.

Answer 1

You can do this:

a = a || 0

…which will convert a from any “falsey” value to 0.

The “falsey” values are:

• false
• null
• undefined
• 0
• "" ^{( empty string )}
• NaN ^{( Not a Number )}

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Or this if you prefer:

a = a ? a : 0;

…which will have the same effect as above.

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If the intent was to test for more than just NaN, then you can do the same, but do a toNumber conversion first.

a = +a || 0

This uses the unary + operator to try to convert a to a number. This has the added benefit of converting things like numeric strings '123' to a number.

The only unexpected thing may be if someone passes an Array that can successfully be converted to a number:

+['123']  // 123

Here we have an Array that has a single member that is a numeric string. It will be successfully converted to a number.