Use the code below.
const abc = '123';
const def = '456';
const varToString = varObj => Object.keys(varObj)[0]
alert ("value of " +varToString({def}) +" is "+ def +" and value of " +varToString({abc})+" is "+abc );
What this basicly does is, you pass the variable to varToString as an object using {variable}. varToString then returns an array with the passed variable as value.
[
"abc"
]
We grab this value using the [0] selector (Object.keys(varObj)[0]). Now it returns
abc
