Javascript 变量 reference/alias

在 javascript 中是否可以以某种方式为本地 var 分配别名/引用？

我的意思是:

function foo() {
var x = 1;
var y = &x;
y++;
alert(x); // prints 2
}

= 编辑 =

在这段代码中是否可以使用 arguments.callee 作为别名? :

function foo() {
arguments.callee.myStaticVar = arguments.callee.myStaticVar || 0;
arguments.callee.myStaticVar++;
return arguments.callee.myStaticVar;
}
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最佳答案

In JavaScript, primitive types such as integers and strings are passed by value whereas objects are passed by reference. So in order to achieve this you need to use an object:

// declare an object with property x
var obj = { x: 1 };
var aliasToObj = obj;
aliasToObj.x ++;
alert( obj.x ); // displays 2
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edit to my previous answer: if you want to count a function's invocations, you might want to try:

var countMe = ( function() {
var c = 0;


return function() {
c++;
return c;
}
})();


alert(countMe()); // Alerts "1"
alert(countMe()); // Alerts "2"

Here, c serves as the counter, and you do not have to use arguments.callee.

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To some degree this is possible, you can create an alias to a variable using closures:

Function.prototype.toString = function() {
return this();
}


var x = 1;
var y = function() { return x }
x++;
alert(y); // prints 2, no need for () because of toString redefinition
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Whether you can alias something depends on the data type. Objects, arrays, and functions will be handled by reference and aliasing is possible. Other types are essentially atomic, and the variable stores the value rather than a reference to a value.

arguments.callee is a function, and therefore you can have a reference to it and modify that shared object.

function foo() {
var self = arguments.callee;
self.myStaticVar = self.myStaticVar || 0;
self.myStaticVar++;
return self.myStaticVar;
}

Note that if in the above code you were to say self = function() {return 42;}; then self would then refer to a different object than arguments.callee, which remains a reference to foo. When you have a compound object, the assignment operator replaces the reference, it does not change the referred object. With atomic values, a case like y++ is equivalent to y = y + 1, which is assigning a 'new' integer to the variable.

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Expanding on user187291's post, you could also use getters/setters to get around having to use functions.

var x = 1;
var ref = {
get x()  { return x; },
set x(v) { x = v; }
};
(ref.x)++;
console.log(x); // prints '2'
x--;
console.log(ref.x); // prints '1'
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in 2019 I need to write minified jquery plugins so I need it too this alias and so testing these examples and others ,from other sources,I found a way without copy in the memory of whe entire object ,but creating only a reference. I tested this already with firefox and watching task manager's tab memory on firefox before. The code is:

var {p: d} ={p: document};
console.log(d.body);

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