add无加号

gistfile1.js

function add(a,b){

    var a = a.toString(2),
        b = b.toString(2),
        max = a.length > b.length ? a.length : b.length,
        result = "",
        res = ["000","110","101","011","001","111","100","010"],
        isCarry = [1,2,3,5],
        carry = "0";

    a = (Array(max).join("0") + a).slice(-max);
    b = (Array(max).join("0") + b).slice(-max);

    console.log(a,b);    
    var _add = function(a,b) {
        
        var i, j, name, index, value;

        i = a.slice(-1);
        j = b.slice(-1);

        name = i + j + carry;
        index = res.indexOf(name); // 结果的index
        carry = isCarry.indexOf(index) > -1 ? "1" : "0";
        value = index > 3 ? "1" : "0";

        result = value + result;
        if(a.length === 1) return result;
        a = a.slice(0,-1);
        b = b.slice(0,-1);
        
        return _add(a,b);
    };

    return parseInt(_add(a,b),2);
}

增加注释

function add(a,b){

    var a = a.toString(2),
        b = b.toString(2),
        max = a.length > b.length ? a.length : b.length,
        result = "",
        res = ["000","110","101","011","001","111","100","010"],     // 前4个值为0 后4个值为1
        isCarry = [1,2,3,5],                                         // 是否进位
        carry = "0";

    // 前位补0
    a = (Array(max).join("0") + a).slice(-max);
    b = (Array(max).join("0") + b).slice(-max);

    var _add = function(a,b) {

        var i, j, name, index, value;

        i = a.slice(-1);
        j = b.slice(-1);

        name = i + j + carry;
        index = res.indexOf(name);                       // 结果的index
        carry = isCarry.indexOf(index) > -1 ? "1" : "0"; // 检测是否有进位
        value = index > 3 ? "1" : "0";                   // 如果大于3，则值为1

        result = value + result;

        // 如果是一位数跳出循环
        if(a.length === 1) return result;

        // 去掉最后一位
        a = a.slice(0,-1);
        b = b.slice(0,-1);

        return _add(a,b);
    };

    return parseInt(_add(a,b),2);
}