Computed Property Names in JavaScript

This is part of our Modern JavaScript course. Check it out if you like this post.

ES6’s “Computed Property Names” feature allows you to have an expression (a piece of code that results in a single value like a variable or function invocation) be computed as a property name on an object.

For example, say you wanted to create a function that took in two arguments (key, value) and returned an object using those arguments. Before Computed Property Names, because the property name on the object was a variable (key), you’d have to create the object first, then use bracket notation to assign that property to the value.

function objectify (key, value) {
  let obj = {}
  obj[key] = value
  return obj
}

objectify('name', 'Tyler') // { name: 'Tyler' }

However, now with Computed Property Names, you can use object literal notation to assign the expression as a property on the object without having to create it first. So the code above can now be rewritten like this.

function objectify (key, value) {
  return {
    [key]: value
  }
}

objectify('name', 'Tyler') // { name: 'Tyler' }

Where key can be any expression as long as it’s wrapped in brackets, [].

This is part of our Modern JavaScript course. Check it out if you like this post.

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