Question

在这种情况下，如何模拟goto编程结构？

$.fn.hierarchy = function(info, ret) {
    if (info.constructor !== Object) {
        info = {children: info};
        goto label1; // Illegal JavaScript
    }

    if (!info.children) {
        info.children = [];
        goto label2; // Illegal JavaScript
    }

    label1:
    if (info.children.constructor !== Array)
        info.children = [info.children];

    label2:
    /*
    // Forget this code. It's irrelevant to my specific problem
    // (which is that JS doens't allow non-nested conditionals)
    //  and caused much confusion.
    if (!info.tagc)
        info.tagc = info.tag || 'div';
    */

我知道我可以将这些goto的 ONE 作为else子句实现：

$.fn.hierarchy = function(info, ret) {
    if (info.constructor !== Object) {
        info = {children: info};
        //goto label1;
    }

    else if (!info.children) {
        info.children = [];
        goto label2; // Illegal JavaScript
    }

    //label1:
    if (info.children.constructor !== Array)
        info.children = [info.children];

    label2:
    /*
    // Forget this code. It's irrelevant to my specific problem
    // (which is that JS doens't allow non-nested conditionals)
    //  and caused much confusion.
    if (!info.tagc)
        info.tagc = info.tag || 'div';
    */

或者：

$.fn.hierarchy = function(info, ret) {
    if (info.constructor !== Object) {
        info = {children: info};
        goto label1; // Illegal JavaScript
    }

    if (!info.children) {
        info.children = [];
        //goto label2;
    }

    else {
        label1:
        if (info.children.constructor !== Array)
            info.children = [info.children];
    }

    //label2:
    /*
    // Forget this code. It's irrelevant to my specific problem
    // (which is that JS doens't allow non-nested conditionals)
    //  and caused much confusion.
    if (!info.tagc)
        info.tagc = info.tag || 'div';
    */

但我希望两个 goto。而且，不，我不想要额外的标志。

修改

@Luis Espinal：您提出的解决方案不起作用。如果info为{children: 'a'}，则您的程序无法将info.children转换为[a]。

$.fn.hierarchy = function(info, ret) {
    if (info.constructor !== Object) {
        info = {children: info};
        // goto label1; // Illegal JavaScript
        // label1:
        if (info.children.constructor !== Array){
            info.children = [info.children];
        }
    }
    else if (!info.children) {
        info.children = [];
        // goto label2; // Illegal JavaScript
        // label2:
        /*
        // Wrong. This has to be placed outside all of this.
        if (!info.tagc)
        {
            info.tagc = info.tag || 'div';
        }
        */
    }
    /* the following code is missing:

    else {
        // Handles the case when info.constructor === Object
        // from the beginning
        // AND
        // info.children isn't an array
        if (info.children.constructor !== Array)
            info.children = [info.children];
    }
    */

编辑：有些人似乎认为第四个条件与我的问题有关。问题实际上是我不能做到以下几点：

If condition1 Then action1
If !condition1 && condition2 Then action2
If !condition2 && condition3 && regardlessOf(condition1) Then action3

不使用标志（临时布尔变量）。

基本上如果condition1为真，我就不必测试condition2，如果condition2为真，我就不必测试condition3 }。但是，如果condition1 && !condition2，我可能需要测试condition3。

Answer 1

可能会将标签更改为函数，并将其更改为setTimeout（functionname，0）

例如，而不是：

label1:
    // do something
    goto label2

label2:
    // do something
    goto label1

尝试这样的事情：

function label1 () {
    // do something
    setTimeout(label2, 0);
    return; // may be needed if not at the end of function
}

function label2 () {
    // do something
    setTimeout(label1, 0);
    return; // may be needed if not at the end of function
}

（你必须使用超时，因为第一个JavaScript不优化尾调用（第二个），第二个因为你不想阻止浏览器而超时为0会使你的回调在事件循环结束时）

Answer 2

除非我的眼睛失败或者我错过了一个模糊的副作用，否则第一个转向的例子相当于以下基于if-else的版本（保佑1960年代的结构化编程结构）：

$.fn.hierarchy = function(info, ret) {
    if (info.constructor !== Object) {
        info = {children: info};
        // goto label1; // Illegal JavaScript
        // label1:
        if (info.children.constructor !== Array){
            info.children = [info.children];
        }
    }
    else if (!info.children) {
        info.children = [];
        // goto label2; // Illegal JavaScript
        // label2:
        if (!info.tagc)
        {
            info.tagc = info.tag || 'div';
        }
    }

Answer 3

JavaScript确实有一个break标签语句，可用于提前退出任何代码块。我相信如果您做了类似的事情，那么考虑到您的第一个代码片段，您将获得所需的效果：

var ft = function(info, ret) {
    label2: {
        label1: {
            if (info.constructor !== Object) {
                info = {children: info};
                break label1;
            }
            else if (!info.children) {
                info.children = [];
                break label2;
            }
        }
        //label1:
        if (info.children.constructor !== Array)
            info.children = [info.children];
    }
    // label2:
    /*
    // Forget this code. It's irrelevant to my specific problem
    // (which is that JS doens't allow non-nested conditionals)
    //  and caused much confusion.
    if (!info.tagc)
        info.tagc = info.tag || 'div';
    */
};

Break标签实际上不是很好，并且不允许你写那种goto意大利面条。它有点结构化，因为它只是提前退出当前块，所以你跳转到label1之后就无法避免label2处理，但是你的原始代码片段却没有，所以这可能会满足你的目标。

Answer 4

您的函数具有非平面控制流程图，因此无法使用结构化编程逻辑实现。如果您关注速度，最好的办法是复制label 1并按如下方式构建代码：

$.fn.hierarchy = function(info, ret) {
    if (info.constructor !== Object) {
        info = {children: info};
        //goto label1; // Illegal JavaScript
        //label1:
        if (info.children.constructor !== Array)
        {info.children = [info.children];}
    }
    else{
        if (!info.children) {
            info.children = [];
            //goto label2; // Illegal JavaScript
        }
        else{
            //label1:
            if (info.children.constructor !== Array)
            {info.children = [info.children];}
        }
    }

    //label2:
    if (!info.tagc)
    {info.tagc = info.tag || 'div';}
};

Answer 5

也许是这样的？

  $.fn.hierarchy = function(info, ret) {
    if(((info.constructor !== Object && info = {children: info}) ||
      (!!info.children || (info.children = [] && false))) &&
      /* label1: */
      info.children.constructor !== Array) {
      info.children = [info.children];      
    }

    /* label2: */
    /*
    // Forget this code. It's irrelevant to my specific problem
    // (which is that JS doesn't allow non-nested conditionals)
    //  and caused much confusion.
    if (!info.tagc) {
      info.tagc = info.tag || 'div';
    }

绕过JavaScript缺少goto而没有额外的标志

5 个答案: