functs.js
function add(...f) {
    if(Array.isArray(f[0])) {
        f = f[0];
    }
    f = f.filter((f) => {
        return typeof f === 'function';
    });
    this._f.push.apply(this._f, f);
    return f;
}
function add(...f) {
    if(Array.isArray(f[0])) {
        f = f[0];
    }
    f = f.filter((f) => {
        return typeof f === 'function';
    });
    this._f.push.apply(this._f, f);
    return f;
}
function add ( ... f ) { if ( Array . isArray ( f [ 0 ] ) ) { f = f [ 0 ] ; } f = f . filter ( ( f ) => { return typeof f === 'function' ; } ) ; this . _f . push . apply ( this . _f , f ) ; return f ; }
add functions to the functs-object
@param {...function|function[]} f - functions to be added
@returns {function[]}
add functions to the functs - object