reliable way to check if a value is a NaN or not

isValueNaN.js

function isValueNaN(value) {
    if(typeof value === "string") {
        value = String(value).trim().length < 1 ? NaN : value;
    }
    
    // Coerce to number (same as global isNaN behavior)
    const num = Number(value);
    // NaN is the only value not equal to itself
    return num !== num;
}

const test = [
    "",
    " ",
    "1.23",
    "123ABC",
    12,
    NaN,
];

for(const item of test) {
    console.log(`Is "${item}" a NaN?: ${isValueNaN(item)}`);
}