Javascript Basics
早该写没有写笔记，为了避免忘记了学过什么还是写一下笔记好了_(:з」∠)_其实我已经忘了(._.)
Variables is always start with ‘var’
var msg = "hi";
Dynamically typed language: No type needed
function a(x, y){...} // arguments without 'var', if arguments are redundant, it won't cause error but not used
var a = function (){} // the same as above, a is a function
Scope chain: Referenced(not defined) var will be searched for in its current scope first, if not found then outer scope will be searched unitl go to the Global scope. If not found at last, it is undefined.
Types: 6 primitive and 1 Object
Object type: a collection of name/value pairs.
Primitive: single, immutable value -> Boolean, Undefined, Null, Number(always double precision 64 bit floating point), String, Symbol
Primitives are passed by value, objects are passed by reference
Function constructors:
// Function constructos, always use name begin with Uppercase
function Circle (radius){
this.r = radius;
// doesn't return anything
this.getArea = // shuold not put here
function() {return Math.PI*Math.pow(this.r, 2);};
}
// should put here, same memory space
Circle.proptype.getArea =
function(){return Math.PI*Math.pow(this.r, 2);};
var myCircle = new Circle(10); // a new object
console.log(myCircle); // Circle{r: 10}
console.log(myCircle.getArea()); // 314.15926....
JS & HTML
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<script src="js/script1.js"></script>
<script src="js/script2.js"></script>
<script src="js/script3.js"></script>
</head>
<body>
<h1>╮(╯▽╰)╭</h1>
</body>
</html>
Script1/2/3 will overwrite vars in gloabl scope and load vars in gload scope.
Fake Namespaces: -> the variables function refers to can be defined in separate files and won’t influence each other.
Immediately Invoked Function Expression: 自执行
(function (name){
var name = name;
function print(){console.log("Hello"+ this.name);}
})();
// pass to the window object
// so the outside and inside will not collide
(function (window) {
var johnGreeter = {};
johnGreeter.name = "John";
var greeting = "Hi ";
johnGreeter.sayHi = function () {
console.log(greeting + johnGreeter.name);
}
window.johnGreeter = johnGreeter;
})(window);
又一个勉强完成