React.js right way to iterate over object instead of Object.entries

a = { 
  a: 1,
  b: 2,
  c: 3
}

Object.keys(a).map(function(keyName, keyIndex) {
  // use keyName to get current key's name
  // and a[keyName] to get its value
})

A newer version, using destructuring and arrow functions. I'd use this one for new code:

a = { 
  a: 1,
  b: 2,
  c: 3
}

Object.entries(a).map(([key, value]) => {
    // Pretty straightforward - use key for the key and value for the value.
    // Just to clarify: unlike object destructuring, the parameter names don't matter here.
})

Complete function render in react

const renderbase = ({datalist}) => {
        if(datalist){
            return  Object.keys(datalist).map((item,index) => {
                return(
                  <option value={datalist[item].code} key={index}>
                      {datalist[item].symbol}
                  </option>
                )
            })
        }  
    }