Say you have this object:

const dog = {
  name: 'Roger'
}

To get the value of the name property, you can use the dot syntax, like this:

dog.name

Or you can use the square brackets property accessor syntax:

dog['name']

This is especially useful when a property has not a valid variable name, like the name:

const dog = {
  'the name': 'Roger'
}

dog['the name']

and it’s also very useful when you don’t know the property name beforehand, and you evaluate it programmatically, like in this example that loops through the object property names:

const dog = {
  'the name': 'Roger'
}

for (const [key, value] of Object.entries(dog)) {
  console.log(value)
}