Data Types and Comparisons
JavaScript Data Types
- OBJECTS
{ }- can be as complex as you want
Example:
var todoList = {
todos: [],
addTodo: function(todoText) {
this.todos.push({
todoText: todoText,
completed: false
});
}
};
- PRIMITIVES - building blocks
- String -
This is a string! - Number -
1, 2, 3, 4 ... - Boolean -
trueorfalse - Undefined - a value that hasn’t been set
- Null -
Nothing
- String -
Comparisons with PRIMITIVES (Values)
Strings
> 'john' === 'john';
true
> 'john1' === 'john';
false
Numbers
> 1 === 1;
true
> 1 === 2;
false
> 36 === '36';
false
Booleans
> true === true;
true
> true === false;
false
> false === false;
true
Undefined and Null
> undefined === undefined;
true
> null === null;
true
Comparisons of OBJECTS (References)
The following examples are FALSE, because the REFERENCES (addresses in memory) differ for each object.
> {} === {}
false
> [1, 2, 3] === [1, 2, 3]
false
The examples below are TRUE, because the REFERENCES (addresses in memory) for the VARIABLES are the same.
> var arrayOne = [1, 2, 3];
> arrayOne;
[1, 2, 3]
// arrayOne (reference) === arrayOne (reference)
> arrayOne === arrayOne;
true
> var objectOne = {};
// objectOne (reference) === objectOne (reference)
> objectOne === objectOne;
true
Additional code examples…
/* ------ Example 1 ------ */
> var myPrimitive = 10;
> myPrimitive;
10
> var myObject = { name: 'John' };
> myObject.name;
'John'
/* ------ Example 2 ------ */
> var myHouse = { color: 'blue' };
> myHouse.color;
'blue'
// Access the property on an object and change it
> myHouse.color = 'red';
> myHouse.color;
'red'
/* ------ Example 3 ------ */
> var myHouse = { color: 'blue' };
> myHouse.color;
'blue'
> var color = myHouse.color;
> color;
'blue'
> color = 'red';
> color
'red'
/* ------ Example 4 ------ */
> var myHouse1 = { color: 'blue' };
> var myHouse2 = myHouse1;
> myHouse1.color;
'blue'
> myHouse2.color;
'blue'
> myHouse2.color = 'red';
> myHouse1.color;
'red'
> myHouse2.color;
'red'
/* ------ Example 5 ------ */
> var myHouse1 = { color: 'blue' };
> var myHouse2 = { color: 'blue' };
> myHouse2.color = 'red';
> myHouse1.color;
'blue'
> myHouse2.color;
'red'