Page 97 - JavaScript

This returns:

[{
id: 1,
name: "John",
age: 28
},{
id: 2,
name: "Jane",
age: 31
}]

Joining array elements in a string

To join all of an array's elements into a string, you can use the join method:

console.log(["Hello", " ", "world"].join("")); // "Hello world"
console.log([1, 800, 555, 1234].join("-")); // "1-800-555-1234"

As you can see in the second line, items that are not strings will be converted first.

Converting Array-like Objects to Arrays

What are Array-like Objects?

JavaScript has "Array-like Objects", which are Object representations of Arrays with a length
property. For example:

var realArray = ['a', 'b', 'c'];
var arrayLike = {
0: 'a',
1: 'b',
2: 'c',
length: 3
};

Common examples of Array-like Objects are the arguments object in functions and HTMLCollection
or NodeList objects returned from methods like document.getElementsByTagName or
document.querySelectorAll.

However, one key difference between Arrays and Array-like Objects is that Array-like objects
inherit from Object.prototype instead of Array.prototype. This means that Array-like Objects can't
access common Array prototype methods like forEach(), push(), map(), filter(), and slice():

var parent = document.getElementById('myDropdown');
var desiredOption = parent.querySelector('option[value="desired"]');
var domList = parent.children;

domList.indexOf(desiredOption); // Error! indexOf is not defined.
domList.forEach(function() {
arguments.map(/* Stuff here */) // Error! map is not defined.
}); // Error! forEach is not defined.

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