The below function will check if the passed variable is undefined, null an empty array or an empty string.

function isNullOrEmpty(variable) {
        // If the passed value is undefined or null then we can return true
        if(variable === undefined || variable === null)
            return true;

        // If the passed value is an empty array then we can return true
        if(Array.isArray(variable))
            return variable.length === 0;

        // If the passed value is an empty string (once trimmed) then we can return true
        if(typeof variable === "string")
            return variable.trim().length === 0;

        // If all the checks pass then we can return false
        return false;
    }