javascript入门笔记（1）——变量和计算

introduction

- introduction
- 前言
  - JavaScript Display Possibilities
  - variable
  - arithmetic

前言

这几章笔记是看了翁凯老师的网上教程做的，这份教程很基础，没有学过编程的同学也可以轻松学习，并且会根据例子讲很多平常容易弄错的细节语法，而且老师声音很好，像是学过播音，让人容易听得进去课。
课程链接：http://study.163.com/course/courseMain.htm?courseId=195001

记笔记的时候在国外，电脑上装不了中文输入法，只好用英文了，markdown写的，编辑器是stackedit，很好用的一款网页编辑器，推荐。

<body onLoad="alert('hi')">
<script>
document.write('hey');
</script>
</body>

document is an object, write() is an action.
onload is an attribute of body.

notice:
1. two layers of quotation is not valid.
change one to single quotation.
2. semicolon is necessary.

JavaScript Display Possibilities

JavaScript can “display” data in different ways:

Writing into an alert box, using window.alert().
Writing into the HTML output using document.write(). //wipe all contents after click
Writing into an HTML element, using innerHTML.
Writing into the browser console, using console.log().

variable

<body>
<script>
var a = "hello"; //assignment, not equality
document.write(a);
</script>
</body>

the name of the variable can only consist of number, character, and underline.
ps: number can’t be in the first place.

arithmetic

<body>
<script>
var a = "hello"; 
var b ="15";
document.write(a+b);//result is hello15
</script>
</body>

javascript can use “+” to append character strings.

double ” ” writes as single ” ” cuz html

<body>
<script>
var a = "hello"; 
document.write(a >= "gello");//result is true
</script>
</body>

character string can also be compared, usually the value is based on there ASCII code.
order:
number< uppercase character< lower case character;

introduction

前言

JavaScript Display Possibilities

variable

arithmetic

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