[英]Can a variable be made readonly in Node.js
I want to prevent a variable from being changed. 我想防止变量被更改。 Specifically a property of an Object:
具体来说是对象的属性:
var foo = { bar: 'baz' };
// do something to foo to make it readonly
foo.bar = 'boing'; // should throw exception
Can this be done? 可以这样做吗?
You could try 你可以试试
Object.defineProperty(foo, "bar", { writable: false });
and the later assignment either fails silently or, if you are in strict mode, throws an exception (according to David Flanagan's "JavaScript : The Definitive Guide" ). 并且后面的分配要么默默失败,要么在严格模式下抛出异常(根据David Flanagan的“ JavaScript:权威指南”)。
Use a function: 使用功能:
var foo = function() {
var bar = 'baz';
return {
getBar: function() {
return bar;
}
}
}();
In that way foo.bar is undefined, you can only access it through foo.getBar(); 这样,foo.bar是未定义的,您只能通过foo.getBar();来访问它。
Look at this example: 看看这个例子:
var Foo = function(){
this.var1 = "A"; // public
var var2 = "B"; // private
this.getVar2 = function(){ return var2; }
}
var foo = new Foo();
console.log(foo.var1); // will output A
console.log(foo.var2) // undefined
console.log(foo.getVar2()) // will output B
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.