如何在JavaScript中通过引用传递变量?

我有三个变量,我想对它们执行一些操作,所以我想把它们放在一个for循环中,并对每个变量执行操作。

伪代码:

myArray = new Array(var1, var2, var3);
for (var x = 0; x < myArray.length; x++){
    // Do stuff to the array
    makePretty(myArray[x]);
}
// Now do stuff to the updated variables

最好的方法是什么?


当前回答

如果你想通过引用传递变量,一个更好的方法是通过在对象中传递参数,然后使用window开始更改值:

window["varName"] = value;

例子:

// Variables with first values
var x = 1, b = 0, f = 15;


function asByReference (
    argumentHasVars = {},   // Passing variables in object
    newValues = [])         // Pass new values in array
{
    let VarsNames = [];

    // Getting variables names one by one
    for(let name in argumentHasVars)
        VarsNames.push(name);

    // Accessing variables by using window one by one
    for(let i = 0; i < VarsNames.length; i += 1)
        window[VarsNames[i]] = newValues[i]; // Set new value
}

console.log(x, b, f); // Output with first values

asByReference({x, b, f}, [5, 5, 5]); // Passing as by reference

console.log(x, b, f); // Output after changing values

其他回答

撇开“参考资料传递”的讨论不谈,那些仍然在寻找上述问题的解决方案的人可以使用:

const myArray = new Array(var1, var2, var3);
myArray.forEach(var => var = makePretty(var));

我个人不喜欢各种编程语言提供的“引用传递”功能。也许这是因为我刚刚发现函数式编程的概念,但是当我看到函数会产生副作用(比如通过引用来操纵参数)时,我总是起鸡皮疙瘩。我个人强烈拥护“单一责任”原则。

恕我直言,函数应该使用return关键字只返回一个结果/值。我不修改参数/实参,而是返回修改后的参数/实参值,并将任何所需的重赋留给调用代码。

但有时(希望很少),需要从同一个函数返回两个或多个结果值。在这种情况下,我会选择将所有这些结果值包含在单个结构或对象中。同样,处理任何重分配都应该由调用代码来决定。

例子:

假设通过在参数列表中使用'ref'这样的特殊关键字来支持传递参数。我的代码可能是这样的:

//The Function
function doSomething(ref value) {
    value = "Bar";
}

//The Calling Code
var value = "Foo";
doSomething(value);
console.log(value); //Bar

相反,我更喜欢这样做:

//The Function
function doSomething(value) {
    value = "Bar";
    return value;
}

//The Calling Code:
var value = "Foo";
value = doSomething(value); //Reassignment
console.log(value); //Bar

当我需要编写一个返回多个值的函数时,我也不会使用引用传递的参数。所以我会避免这样的代码:

//The Function
function doSomething(ref value) {
    value = "Bar";

    //Do other work
    var otherValue = "Something else";

    return otherValue;
}

//The Calling Code
var value = "Foo";
var otherValue = doSomething(value);
console.log(value); //Bar
console.log(otherValue); //Something else

相反,我实际上更喜欢在对象中返回两个新值,就像这样:

//The Function
function doSomething(value) {
    value = "Bar";

    //Do more work
    var otherValue = "Something else";

    return {
        value: value,
        otherValue: otherValue
    };
}

//The Calling Code:
var value = "Foo";
var result = doSomething(value);
value = result.value; //Reassignment
console.log(value); //Bar
console.log(result.otherValue);

这些代码示例非常简化,但它大致演示了我个人如何处理这些东西。它帮助我把各种责任放在正确的位置。

快乐的编码。:)

简单的对象

函数foo(x) { //使用其他上下文函数 //修改' x '属性,增加值 x.value + +; } //初始化' ref '为对象 Var = { // ' value '在' ref '变量对象中 //初始值为' 1 ' 值:1 }; //用对象值调用函数 foo (ref); //再次调用带有对象值的函数 foo (ref); console.log (ref.value);//打印"3"


自定义对象

对象rvar

/** * Aux function to create by-references variables */ function rvar(name, value, context) { // If `this` is a `rvar` instance if (this instanceof rvar) { // Inside `rvar` context... // Internal object value this.value = value; // Object `name` property Object.defineProperty(this, 'name', { value: name }); // Object `hasValue` property Object.defineProperty(this, 'hasValue', { get: function () { // If the internal object value is not `undefined` return this.value !== undefined; } }); // Copy value constructor for type-check if ((value !== undefined) && (value !== null)) { this.constructor = value.constructor; } // To String method this.toString = function () { // Convert the internal value to string return this.value + ''; }; } else { // Outside `rvar` context... // Initialice `rvar` object if (!rvar.refs) { rvar.refs = {}; } // Initialize context if it is not defined if (!context) { context = this; } // Store variable rvar.refs[name] = new rvar(name, value, context); // Define variable at context Object.defineProperty(context, name, { // Getter get: function () { return rvar.refs[name]; }, // Setter set: function (v) { rvar.refs[name].value = v; }, // Can be overrided? configurable: true }); // Return object reference return context[name]; } } // Variable Declaration // Declare `test_ref` variable rvar('test_ref_1'); // Assign value `5` test_ref_1 = 5; // Or test_ref_1.value = 5; // Or declare and initialize with `5`: rvar('test_ref_2', 5); // ------------------------------ // Test Code // Test Function function Fn1(v) { v.value = 100; } // Test function test(fn) { console.log(fn.toString()); console.info(fn()); } // Declare rvar('test_ref_number'); // First assign test_ref_number = 5; test(() => test_ref_number.value === 5); // Call function with reference Fn1(test_ref_number); test(() => test_ref_number.value === 100); // Increase value test_ref_number++; test(() => test_ref_number.value === 101); // Update value test_ref_number = test_ref_number - 10; test(() => test_ref_number.value === 91);

I've been playing around with syntax to do this sort of thing, but it requires some helpers that are a little unusual. It starts with not using 'var' at all, but a simple 'DECLARE' helper that creates a local variable and defines a scope for it via an anonymous callback. By controlling how variables are declared, we can choose to wrap them into objects so that they can always be passed by reference, essentially. This is similar to one of the Eduardo Cuomo's answer above, but the solution below does not require using strings as variable identifiers. Here's some minimal code to show the concept.

function Wrapper(val){
    this.VAL = val;
}
Wrapper.prototype.toString = function(){
    return this.VAL.toString();
}

function DECLARE(val, callback){
    var valWrapped = new Wrapper(val);    
    callback(valWrapped);
}

function INC(ref){
    if(ref && ref.hasOwnProperty('VAL')){
        ref.VAL++; 
    }
    else{
        ref++;//or maybe throw here instead?
    }

    return ref;
}

DECLARE(5, function(five){ //consider this line the same as 'let five = 5'
console.log("five is now " + five);
INC(five); // increment
console.log("five is incremented to " + five);
});

通过引用传递变量的变通方法:

var a = 1;
inc = function(variableName) {
  window[variableName] += 1;
};

inc('a');

alert(a); // 2

是的,实际上你可以在不访问全局变量的情况下完成:

inc = (function () {
    var variableName = 0;

    var init = function () {
        variableName += 1;
        alert(variableName);
    }

    return init;
})();

inc();