What does the colon ( : ) mean in this javascript line?

Question

What does the \":\" mean in the 3-6th lines below?

function displayError(error) {
    var errorTypes = {
        0: \"Unknown error\",
        1: \"Permissi         


        

Answer 1

That's how you define key value pairs in an object. So errorTypes.2 would return the string "Position is not available".

Answer 2

The variable errorTypes is an object literal. The : separates the object property name (the numbers) from its value. If you are familiar with hash tables in other languages, this structure is a similar concept. Or in PHP, for example, this could be represented as an associative array.

You can do:

var errorTypes = {
    0: "Unknown error",
    1: "Permission denied",
    2: "Position is not available",
    3: "Request timeout"
};

console.log(errorTypes[0]);
// Unknown error

console.log(errorTypes[2]);
// Permission denied

Note that the normal syntax for referencing an object property (using the dot operator) won't work for these numeric properties:

// Won't work for numeric properties
errorTypes.0
SyntaxError: Unexpected number

// Instead use the [] notation
errorTypes[0]

In this instance, since numeric property names were used, the whole thing could have been defined as an array instead and accessed exactly the same way via the [] notation, but with less syntactic control over the keys.

// As an array with the same numeric keys
var errorTypes = [
    "Unknown error",
    "Permission denied",
    "Position is not available",
    "Request timeout"
];
console.log(errorTypes[2]);