此语法在JavaScript中返回{hello：“ world”}的含义是什么[something]

Question

I saw this syntax in some code

   function parseMessage(error) {
    return {
      15: 'Faulted'
    }[error];
  }

I have never seen a function be invoked with an array is that what this means ?

Answer 1

There is no array involved there.

It creates an object, then accesses the value of one of the object's properties by square bracket notation, and then returns that value.

It is equivalent to:

function parseMessage(error) {
   var myData = {
       "15": 'Faulted'
   };
   var result = myData[error];
   return result;
}

Answer 2

The above function is creating an object and then returning value of property using bracket notation

Example: if value of error is 15 then function will return 'Faulted' . See DEMO

Answer 3

this function internally use a JavaScript Object Literal ,

Object literals are used as a means of encapsulating data, enclosing it in a tidy package to minimize the use of global variables which can cause problems when combining code.

Object literals are formed using the following syntax rules:

• A colon separates property name from value.
• A comma separates each name/value pair from the next.
• There should be no comma after the last name/value pair. Most browsers won't object if you add it, but Internet Explorer prior to version 9 will generally trigger an error: 'Expected identifier, string or number'.

As Object literal is usable as a Associative Array