Addition and Subtraction Without Operators in Javascript

withoutOperators.js

function dec2bin(dec){
    "use strict";
    return dec.toString(2);
}


function bin2dec(bin){
    "use strict";
    return parseInt(bin,2);
}

function full32bit(bitComing){
    "use strict";
    let fullWith = bitComing<0?"1":"0";
    bitComing=bitComing.replace('-','');
    let leftFill=[];
    for(var cvb=bitComing.length; cvb<32; cvb++){
        leftFill.push(fullWith)
    }
    leftFill.push(Math.abs(bitComing).toString());
    return leftFill.join('');
}

function MathOp(a,b) {
a = full32bit(dec2bin(a));
b = full32bit(dec2bin(b));



let count="";
let k=0;
for(var xv=32; xv>0; xv--){
    let r1 = Boolean(parseInt(a[xv]));
    let r2 = Boolean(parseInt(b[xv]));
    let c="";
    switch(k){
        case k=0:
            if(!r1 && !r2){c="0"; k=0;}
            else if((r1 && !r2) || (!r1 && r2)){c="1"; k=0;}
            else if(r1 && r2){c="0"; k=1}
            break;

        case k=1:
            if(!r1 && !r2){c="1"; k=0;}
            else if((r1 && !r2) || (!r1 && r2)){c="0"; k=1;}
            else if(r1 && r2){c="1"; k=1}
            break;
    }
    count=c+count;
}
    return bin2dec(count);
}


console.log(MathOp(-4,5));

Try to do Math Operations (adding and subtraction two numbers) wtihout +,-,%,*,/ operators.
Commonly known way is bit operation. I am learning and try to solve.