What is the difference between val?.toLocaleString() and using an if statement to check undefined-CodePudding

I have this:

return '£'   val?.toLocaleString();

to check if val has a value, however I'm not sure how safe this is compared to the following:

if(val) {
    return '£'   val.toLocaleString();
}
return val

Could someone help me breakdown what the differences are here and why one is preferable, if that is the case?

CodePudding user response：

First one if the val is undefined or null it will concate the value of val with undefined

function format(val) {
  return '£'   val?.toLocaleString();
}

console.log(format())
console.log(format(null))
console.log(format(3))

The second one will only make concatenation if val is a truthy value, else will return val as it's

Just keep in mind that zero is a falsy value.

function format(val) {
  if(val) {
    return '£'   val.toLocaleString();
  }
  return val
}

console.log(format())
console.log(format(0))
console.log(format(3))