Skip to content

Latest commit

 

History

History
173 lines (109 loc) · 3.19 KB

data.md

File metadata and controls

173 lines (109 loc) · 3.19 KB
Raw

Data

Type

3 Basic Types

  • Boolean (true or false)
  • Number (1, 47, 3.14159)
  • String ('any "string" of characters')

2 Nothing Types

  • null -> "Intentional Opt Out"
  • undefined -> "Missing"

Why two types for the same concept?

2 Aggregate Types

  • Array -> a list of ordered values
  • Object -> a "bag" of values with String labels

1 Magic Type

  • Function

Boolean

Number

String

null and undefined

Array

Object

Objects are very important and powerful. Below we will start with creating simple objects and work towards building objects that are more complex.

Objects let us store data in much more meaningful and helpful ways, with property names. Each Property of an Object can hold any data-type: Booleans, Numbers, Strings, an Array, an Object, or a Function.

Caveat

Below you may see the term key-value pair, this is just another way of referring to an object's property name (key) and its value.

There may be places where a suggested variable name may have been left out, it is up to you as a programmer to name these variables. Make 'em good!

Also, other the instructions may get vague as you progress through this exercise.

Reference

Js-Basics Slides - Objects Section

Object uses

Two uses:

  1. Record of structured data
  2. Index of key-value pairs (aka. Map)

Record usage

keys are known (static)

Defined ahead of time:

myObject =
  { keyOfNumber: 3,
    keyOfBoolean: true,
    'key-of-string': 'str',
    keyOfObject: { key5: 'nested'},
    keyOfArray: [ 0, 1 ] };

Adding/changing properties after the fact:

myObject.keyOfNumber = 4;
myObject.newKey = 15;

Reading:

console.log(myObject.keyOfNumber);

console.log(myObject['key-of-string']);

Properties and Methods

An object is a collection of properties, and a property is an association between a name (or key) and a value. A property's value can be a function, in which case the property is known as a method.

Example of property:

myArr = [ 1, 2, 3 ];
myArr.length  // <- length is property

Example of method:

console.log  // <- log is method

Method declaration

(With anonymous function):

myObject = {
    myMethod: function (x) {
        // do something with x...
    }
};

// OR...

myObject = {};
myObject.myMethod = function (x) {
    // do something with x...
};

Map usage

keys are unknown (dynamic)

Build as you go:

myMap = {};
myKey = 'some string';
myValue = 27;

// assign value for a key
myMap[myKey] = myValue;

// read value for a key
console.log(myMap[myKey]);

Map iteration example: Environment Variables

process.env is just an Object

for (var key in process.env) {
    if (key === 'PATH') {

        var isWin = /^win/.test(process.platform);
        var delimeter = isWin ? ';' : ':';
        var pathElems = process.env.PATH.split(delimeter);

        for (var k = 0; k < pathElems.length; k++) {
            console.log(key, k, pathElems[k]);
        }
    } else {
        console.log(key, process.env[key]);
    }
}

Function

(see logic)