how to combine two arrays into one object with key value pair?

An alternative method would be as shown below. This loops for a.length amount of times, gets the value of a and adds it as a key to c, where the key's value is the value from b. Here is a breakdown of how it works:

For each element in a: if there exists no element in c with the keyname a[i], create the key and set it to the value from b[i]. If the element does already exist in c (then the key must represent an array, not a single item), if that value is a single item, make it an array, and re insert that first value, then in any case, push the new item to that array.

let a = ['name', 'options', 'address', 'options', 'gender', 'options','options']; let b = ['john doe', 'a', 'india', 'b', 'male', 'c', 'd']; let c = {}; for (let i=0; i<a.length; i++) { if (typeof c[a[i]] === 'undefined') { c[a[i]] = b[i]; } else { if (c[a[i]] instanceof Array === false) { c[a[i]] = [c[a[i]]]; } c[a[i]].push(b[i]); } } console.log(c);

 invert(object){ let invertedObject ={}; for(let key in object){ const originalValue = object[key]; invertedObject = {originalValue : key} } return invertedObject } 

let a = ['name', 'options', 'address', 'options', 'gender', 'options']; let b = ['john doe', 'a', 'india', 'b', 'male', 'c']; let r = a.reduce((o,c,i) => {o[c] = o[c] ? o[c] + ", " + b[i]:b[i]; return o;}, []) console.log(r);