JavaScript Lazy单件 - 延迟到第一次访问才执行构造函数

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var LazySingleton = function(){     var val = 1, _instance;     var lazy_init = function(){         alert('Lazy init, exec no more than once.');         return {             getVal : function(){ return val; },             setVal : function(v){ val = v; }         };     };     var init = function(){         init = function(){ return _instance; };         return _instance = lazy_init();     };     return {         getInstance : function(){ return init(); }     }; }();   alert('load before lazy init.'); var ls1 = LazySingleton.getInstance(); // will exec lazy init alert(ls1.getVal()); // 1 ls1.setVal(5);   var ls2 = LazySingleton.getInstance(); // won't exec lazy init alert(ls2.getVal()); // 5 alert(ls1 == ls2); // true alert(ls1 === ls2); // true

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