SOURCE

function omit(obj, keys){
    let ans = {};
    Object.getOwnPropertyNames(obj).forEach(function(key){
        let flag = 0;
        for (let i = 0; i < keys.length; i++) {
            if (key == keys[i]) flag = 1;
        }
        if(flag == 0)
            ans[key] = obj[key];
    })
    return ans;
}

const obj = {  
    a: 1,  
    b: 2,  
    c: 3,  
    d: 4  
}

console.log(temp = omit(obj, ['a', 'b']));