How to convert a value into String in JS?

Sep 09, 2022

As you can see, there are completely different mechanisms for trying to convert a value into a string. So how do we choose?

  • when we want to convert¬†null¬†and¬†undefined¬†to a string, we often want it to return an empty string.
  • when we turn an array and a plain object into a string, we often want to use¬†JSON.stringify.
  • If the object‚Äôs¬†toString¬†method is overridden, then we want to use¬†String().
  • In other cases,¬†String()¬†is used to convert the value to a String.
function isPlainObject(obj) {
  return === "[object Object]";

function toString(val) {
  if (val === null || val === undefined) return "";
  if (Array.isArray(val)) return JSON.stringify(val);
  if (isPlainObject(val) && val.toString === Object.prototype.toString)
    return JSON.stringify(val); // other cases
  return String(val);

Also to join the elements in an array, instead of using join(',') we can use String([1,2,3])