var r = '123456789'.split("").reverse().reduce(function(pre, current){
        pre = (pre.constructor == Array) ? pre : [pre]; // required for the first element
        return [...pre.map(function(item){
            return ["", "+", "-"].reduce(function(carry, op) {
                return [...carry,
                    ("-" + current + op + item).replace(/[-,+][-,+]/g, "-"),
                    (current + op + item).replace(/[-,+][-,+]/g, "-")
                ];
            },[]).filter(function(item, pos, self) { // required to remove duplicates
                return self.indexOf(item) == pos;
            });
        }).reduce(function(p, c) {
            return [...p, ...c];
        }, [])];
    }).filter(function(item, pos, self) { // required to remove duplicates
        return self.indexOf(item) == pos;
    });

    console.log(r.length);
    console.log(r.filter(function(val){
        return (eval(val) === 100);
    }));