locutus/esm/php/math/is_nan.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function is_nan(val) {
    //  discuss at: https://locutus.io/php/is_nan/
    // original by: Onno Marsman (https://twitter.com/onnomarsman)
    //    input by: Robin
    //   example 1: is_nan(NaN)
    //   returns 1: true
    //   example 2: is_nan(0)
    //   returns 2: false
    let warningType = '';
    if (typeof val === 'number' && isNaN(val)) {
        return true;
    }
    // Some errors for maximum PHP compatibility
    if (typeof val === 'object') {
        warningType = Array.isArray(val) ? 'array' : 'object';
    }
    else if (typeof val === 'string' && !/^[+-]?\d/.test(val)) {
        // simulate PHP's behaviour: '-9a' doesn't give a warning, but 'a9' does.
        warningType = 'string';
    }
    if (warningType) {
        throw new Error('Warning: is_nan() expects parameter 1 to be double, ' + warningType + ' given');
    }
    return false;
}