A container for data that's stored as key-value pairs.
Objects help to organize related data of any type, including other objects. A value stored in an object can be accessed by name, called its key. Each key-value pair is called a "property." Objects are similar to dictionaries in Python and maps in Java and Ruby.
For example, an object could contain the location, size, and appearance of a dog:
// Declare the dog variable and assign it an object.
let dog = { x: 50, y: 50, size: 20, emoji: '🐶' };
// Style the text.
textAlign(CENTER, CENTER);
textSize(dog.size);
// Draw the dog.
text(dog.emoji, dog.x, dog.y);
The variable dog
is assigned an object with four properties. Objects are declared with curly braces {}
. Values can be accessed using the dot operator, as in dog.size
. In the example above, the key size
corresponds to the value 20
. Objects can also be empty to start:
// Declare a cat variable and assign it an empty object.
let cat = {};
// Add properties to the object.
cat.x = 50;
cat.y = 50;
cat.size = 20;
cat.emoji = '🐱';
// Style the text.
textAlign(CENTER, CENTER);
textSize(cat.size);
// Draw the cat.
text(cat.emoji, cat.x, cat.y);
An object's data can be updated while a sketch runs. For example, the cat
could run away from the dog
by updating its location:
// Run to the right.
cat.x += 5;
If needed, an object's values can be accessed using square brackets []
and strings instead of dot notation:
// Run to the right.
cat["x"] += 5;
This syntax can be helpful when the key's name has spaces, as in cat['height (m)']
.
示例
相关参考
stringify
From the MDN entry: The JSON.stringify() method converts a JavaScript object or value to a JSON string.
log
Prints a message to your browser's web console.
===
The strict equality operator === checks to see if two values are equal and of the same type.
console
Prints a message to the web browser's console.