JS 基础篇(单例模式)
以弹窗为例 < ! DOCTYPE html > < html lang = "en" > < head > < meta charset = "UTF-8" > < meta name = "viewport" content = "width=device-width, initial-scale=1.0" > < meta http - equiv = "X-UA-Compatible" content = "ie=edge" > < title > 单例模式 < / title > < / head > < body > < button type = "button" id = "btnpop" > 弹出 < / button > < button type = "button" id = "btnframe" > iframe < / button > < script > //把变 的部分封装，不变的隔离 ，开发-封闭原则 function createEl ( fn ) { var result ; return function ( ) { if ( ! result ) { result = fn . apply ( this , arguments ) ; } return result ; } } function createWindow ( ) {