https://github.com/nodejh/professional_javascript_notes
📔 Professional JavaScript for Web Developers Reading Notes
https://github.com/nodejh/professional_javascript_notes
Last synced: 5 months ago
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📔 Professional JavaScript for Web Developers Reading Notes
- Host: GitHub
- URL: https://github.com/nodejh/professional_javascript_notes
- Owner: nodejh
- Created: 2016-12-12T18:01:45.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2017-03-24T06:42:46.000Z (almost 9 years ago)
- Last Synced: 2025-10-28T10:04:01.226Z (5 months ago)
- Language: JavaScript
- Size: 19.5 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# 《JavaScript高级程序设计读书笔记》
## TODO
+ 8.1.4 窗口大小，书上讲得不够清楚
## ISSUE
### P72 [已解决]
主要是 JS 传递参数的方式。
[https://github.com/nodejh/nodejh.github.io/issues/32](https://github.com/nodejh/nodejh.github.io/issues/32)
```
function setName(obj) {
obj.name = 'nodejh';
obj = new Object();
obj.name = 'jh';
}
var person = new Object();
setName(person);
alert(person.name); // nodejh
```
为什么是 nodejh？
```
function addTen(num) {
num += 10;
return num;
}
var count = 20;
var result = addTen(count);
alert(count); // 20, 没有变化
alert(result); // 30
```
## 知识点
#### 闭包
+ [js闭包,垃圾回收,内存泄漏](https://segmentfault.com/a/1190000004682028)
```
function f1() {
var res = new Array();
for(var i=0;i<10;i++){
res[i] = function() {
alert(i);
};
}
return res;
}
var f2 = f1();
var f2 = f1();
f2[0]();//alert 10
//并不会返回一次弹出0-9的函数数组，而是弹出10个10的函数数组,因为res中每个函数的作用域中都保存着f1()的活动对象，引用的是同一个变量i，当f1()返回后i的值为10
```
```
function f1() {
var res = new Array();
for(var i=0;i<10;i++){
res[i] = (function(num) {
return function (){
alert(num);
}
})(i);//函数参数按值传递
}
return res;
}
var f2 = f1();
var f2 = f1();
f2[0]();//alert 0
```
#### 内存回收
```
window.onload = function(){
var ele = document.getElementById("id");
ele.onclick = function(){
alert(ele.id);
}
}
```
循环引用。
```
ele.onclick = function(){
alert(ele.id);
}
```
解决办法：
```
window.onload = function(){
var ele = document.getElementById("id");
var id = ele.id; //解除循环引用
ele.onclick = function(){
alert(id);
}
ele = null; // 将闭包引用的外部函数中活动对象清除
}
```