js--函数柯里化

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function add(...args) {
    const iterator = (...rest) => {
        args = [...rest, ...args];
        return iterator;
    };
    iterator.toString = () => args.reduce((a, b) => a + b);
    return iterator;
}

add(1, 2)(3)(4);//10
add(1)(2)(3)(4);//10
add(1,2,3,4);//10