Question

这是一个学术问题,是为了澄清我对 Java本的理解。

功能物体一旦产生即可被分配为属性。然而,在一个步骤中能否形成具有属性的功能目标?

例如,

function someFunction(){
}

var someFunctionObject=someFunction;


someFunctionObject.attr1="attr 1";

alert(someFunctionObject.attr1); /* "attr 1"

在此,在提出标的后,第二步中正添加属性。能否在一个步骤中做到这一点?

Answer 1

答案是没有的。解释如下。

你的法典的最终结果如下:

var myFunctionObject = {
    prop1:  foo ,
    prop2:  bar ,
    construct: "alert( function body )"
};
myFunctionObject(); // should alert
myFunctionObject.prop1; //  foo

功能定义/声明实际上非常相似,它产生一项标注,将[建筑]财产交给实际机构。但是,这只是一个执行细节,你不能单独获取或确定[建筑]财产,因此,你无法在一戈内界定其他财产(这将需要额外的合成物,而且不存在)。

但是,如果符合你需要,你可以从职能范围内确定财产。例如,这样做有助于打下:

function getSomething() {
    if (getSomething.prop) return getSomething.prop;
    return getSomething.prop = fetchResource();
}

Answer 2

这样做的最佳方式是将一个指定的职能分配到如下变量:

var someFunctionObject = (function someFunction() {
    if (!someFunction.attr1) {
        someFunction.attr1 = "attr1";
        return someFunction;
    }
    // extra processing
}());

alert(someFunctionObject.attr1);

这增加了以下好处,即如果某人删除了 at1财产,则将随后重新开始:

delete someFunctionObject.attr1; // deleted
someFunctionObject();            // reinitialized
alert(someFunctionObject.attr1); // back to square one

撰写上述建筑的更好办法是:

var someFunctionObject = (function someFunction() {
    if (someFunction.attr1) {
        // extra processing
    } else {
        someFunction.attr1 = "attr1";
        return someFunction;
    }
}());

This is both faster and better because:

We don t use the logical NOT operator. This saves an instruction to execute when interpreted. Logical NOT doesn t coerce, so using it has no benefits.
The function object is usually only initialized once, so logically the initialization should come last as it ll be rarely called.

Answer 3

function someFunction(attr1){
  this.attr1 = attr1; 
}

var someFunctionObject = new someFunction( attr 1 );
console.log( someFunctionObject.attr1 );

Answer 4

var someFunc = new function(attr1){
  this.attr1 = attr1; 
}("blah");

alert(someFunc.attr1);

这是一个步骤,但不是一个非常有益的构造。

Answer 5

你在座右铭上只剩下了一点(但很重要)。你在样本代码中所做的事情是发挥作用的,然后将这一功能指定为另一个物体上的财产(susactObject)。

What you did in literal terms looks like this:

var someFunctionObject = {
    someFunction : function(){},
    attr1 : "attr 1"
}

This results in one object (someFunctionObject, which is poorly named at this point, as it s just a regular object) with two properties assigned to it: one string, and one function.

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