Javascript Objects Notes
As javascript objects are used so often in javascript i thought i would write an overview and some notes on how they work, well how they work for me anyway. I guess how they work for me should be similar to how they just work, so should be good.
What is a Javascript Object?
- A javscript object is a collection of named values.
- Objects is an unordered collection of key value pairs.
- Javascript Objects are like an array, but not actually an array.
An example of a Javascript Object
Javascript
const my_object = {
"my_object_1": "value1",
"my_object_2": "value2",
"my_object_3": "value3"
}Accessing Properties of an Object
Lets take the my_object and access value2 from it.
You can do this with : objectName.property
or like this
objectName["property"]
Javascript
console.log(my_object.my_object_2);Convert an Object to An Array
You can convert your javascript object into an array with Object.values(objectName);
Javascript
/* an array of the object called my_object_array */
const my_object_array = Object.values(my_object);
console.log(my_object_array);Loop throught the new array
Usually i forget how to do this, so i thought i would add it here to see if it jogs my memory.
The array is now called my_object_array
This seems to work:
Javascript
/* foreach on the array function */
let out = "";
my_object_array.forEach(do_stuff_function);
function do_stuff_function(value, index, array) {
out += "value: " + value + ", index: " + index + "array: " + array;
}
console.log(out);Object Methods
You can add things like functions inside objects, which makes them even more useful than arrays.
add code and example...
Constructor
A blue print for creating objects.
Javascript
const my_object = {
"my_object_1": "value1",
"my_object_2": "value2",
"my_object_3": "value3"
}
console.table(my_object);
// console.log the value of my_object.my_object_2
console.log(my_object.my_object_2);
// console.log the value of objectName["property"]
console.log( my_object["my_object_2"] );
// an array of the object called my_object_array
const my_object_array = Object.values(my_object);
console.log(my_object_array);
// foreach on the array function
let out = "";
my_object_array.forEach(do_stuff_function);
function do_stuff_function(value, index, array) {
out += "value: " + value + ", index: " + index + "array: " + array;
}
console.log(out);View Statistics
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Random Quote
"Olivia, my eldest daughter, caught measles when she was seven years old. As the illness took its usual course I can remember reading to her often in bed and not feeling particularly alarmed about it. Then one morning, when she was well on the road to recovery, I was sitting on her bed showing her how to fashion little animals out of coloured pipe-cleaners, and when it came to her turn to make one herself, I noticed that her fingers and her mind were not working together and she couldn’t do anything. 'Are you feeling all right?' I asked her. 'I feel all sleepy,' she said. In an hour, she was unconscious. In twelve hours she was dead. The measles had turned into a terrible thing called measles encephalitis and there was nothing the doctors could do to save her. That was...in 1962, but even now, if a child with measles happens to develop the same deadly reaction from measles as Olivia did, there would still be nothing the doctors could do to help her. On the other hand, there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised against measles. ...I dedicated two of my books to Olivia, the first was ‘James and the Giant Peach’. That was when she was still alive. The second was ‘The BFG’, dedicated to her memory after she had died from measles. You will see her name at the beginning of each of these books. And I know how happy she would be if only she could know that her death had helped to save a good deal of illness and death among other children."
I just checked google books for BFG, and the dedication is there.
https://www.google.com.au/books/edition/_/quybcXrFhCIC?hl=en&gbpv=1
Roald Dahl, 1986
