function ClassA(sColor) {
this.color = sColor;
}
ClassA.prototype.sayColor = function () {
alert(this.color);
};
function ClassB(sColor, sName) {
ClassA.call(this, sColor);
this.name = sName;
}
ClassB.prototype = new ClassA();
ClassB.prototype.sayName = function () {
alert(this.name);
};
var objA = new ClassA("blue");
var objB = new ClassB("red", "John");
objA.sayColor(); //输出 "blue"
objB.sayColor(); //输出 "red"
objB.sayName(); //输出 "John"
10、call、apply和bind：call和apply的用途都是用来调用当前函数，且用法相似，它们的第一个参数都用作 this 对象，但其他参数call要分开列举，而apply要以一个数组形式传递；bind给当前函数定义预设参数后返回这个新的函数(初始化参数改造后的原函数拷贝)，其中预设参数的第一个参数是this指定(当使用new 操作符调用新函数时，该this指定无效)，新函数调用时传递的参数将位于预设参数之后与预设参数一起构成其全部参数，bind最简单的用法是让一个函数不论怎么调用都有同样的 this 值。下边的list()也称偏函数(Partial Functions)：
function list() {
return Array.prototype.slice.call(arguments);
}
var list1 = list(1, 2, 3); // [1, 2, 3]
// Create a function with a preset leading argument
var leadingThirtysevenList = list.bind(undefined, 37);
var list2 = leadingThirtysevenList(); // [37]
var list3 = leadingThirtysevenList(1, 2, 3); // [37, 1, 2, 3]
11、Memoization技术：替代函数中太多的递归调用，是一种可以缓存之前运算结果的技术，这样我们就不需要重新计算那些已经计算过的结果。In computing, memoization or memoisation is an optimization technique used primarily to speed up computer programs by storing the results of expensive function calls and returning the cached result when the same inputs occur again. Although related to caching, memoization refers to a specific case of this optimization, distinguishing it from forms of caching such as buffering or page replacement. In the context of some logic programming languages, memoization is also known as tabling.
function memoizer(fundamental, cache) {
let cache = cache || {},
shell = function(arg) {
if (! (arg in cache)) {
cache[arg] = fundamental(shell, arg);
}
return cache[arg];
};
return shell;
}
14、DocumentFragment：Roughly speaking, a DocumentFragment is a lightweight container that can hold DOM nodes. 在维护页面DOM树时，使用文档片段document fragments 通常会起到优化性能的作用
let ul = document.getElementsByTagName("ul")[0],
docfrag = document.createDocumentFragment();
const browserList = [
"Internet Explorer",
"Mozilla Firefox",
"Safari",
"Chrome",
"Opera"
];
browserList.forEach((e) => {
let li = document.createElement("li");
li.textContent = e;
docfrag.appendChild(li);
});
ul.appendChild(docfrag);
15、forEach()遍历：另外，适当时候也可以考虑使用for 或 for ... in 或 for ... of 语句结构
1. 数组实例遍历： arr.forEach(function(item, key){ //do some things }) 2. 非数组实例遍历： Array.prototype.forEach.call(obj, function(item, key){ //do some things }) 3. 非数组实例遍历： Array.from(document.body.childNodes[0].attributes).forEach(function(item, key){ //do some things. Array.from()是ES6新增加的 })
16、DOM事件流：Graphical representation of an event dispatched in a DOM tree using the DOM event flow.If the bubbles attribute is set to false, the bubble phase will be skipped, and if stopPropagation() has been called prior to the dispatch, all phases will be skipped.
