# Javascript Notes學習筆記 Source: [JavaScript for Web Designers](https://www.youtube.com/watch?v=ResWVWI333o) By Envato Tuts+ ## 1.Where? - Console on browser - HTML Document (including js tags) ```<script> </script>``` - Using a dedicated JavaScript file Create a new file called OOO.js And in HTML document write down ```<script src="OOO.js"></script>``` ## 2.Variables ### declare ``` var x,y,z;``` - **case sensitive** Estelle is different from estelle. - **Some words has been declare in this language can't be declared** ```(invalid) var var``` - **Input the value** ``` var x; x= 87;``` ## Data type - **string** ``` var name ="Estelle"``` (You can use single quote and double quote.) - **number** ``` var age = 18``` (You can also use float number.) - **boolean** true | false ```var graduated = false;``` - **null** If you wanna delete the content of variable-- use "null". ```var age = null ``` - **undefined** #### typeof In the console, ``` typeof name``` it will output "string" It's a good way to check out the type of a variable. ## Array Let's see an example: ``` var list =["Estelle", "Saki", "Max", "Fei", 123, true];``` or create an empty array: ``` list2 =[];``` or create an array like that: ```list3 = new Array(777, false);``` - The first position of array is from 0, just like C++ or Python. - How many element in this array? ``` list.length ``` - Add new item as the last: ``` list.push("Yay")``` - Add new item as the first: ``` list.unshift()``` - Remove the last item: ``` list.pop()``` - Remove the first item: ``` list.shift()``` - Where is the index? Let's find it out! ```list.indexOf(Estelle)``` And it will display "0". ## Objects