Eval vs IF statements (many IF statements)

问题

This fiddle pretty much explains what I'm looking for. I'm trying to find the simplest way to go about coding something WITHOUT using eval. I can do it without eval but I think I will have to write 1000s of IF statements. Or is there another way?

http://jsfiddle.net/243rz8eq/9/

HTML

Eval way...<br>
<a href="javascript:core.launch('wins.a({x:1})');">Window-A</a><br>
<a href="javascript:core.launch('wins.b({x:1})');">Window-B</a><br>
<a href="javascript:core.launch('wins.c({x:1})');">Window-C</a><br><br>

Non-Eval way.  Requires if statement for each window (there will be thousands).  Or is there a simpler way I'm not seeing?<br>
<a href="javascript:core.launch_no_eval('window_a');">Window-A</a><br>
<a href="javascript:core.launch_no_eval('window_b');">Window-B</a><br>
<a href="javascript:core.launch_no_eval('window_c');">Window-C</a><br><br>

JavaScript

window.core = {
    launch: function(obj_string) {
        //we init a blank dhtmlxwindow and do some other things here, then...
        var x = eval("new " + obj_string); //fill dhtmlxwindow with proper content
    },
    launch_no_eval: function(id) {
        //we init a blank dhtmlxwindow and do some other things here, then...
        if (id==="window_a") var x = wins.a({x:1}); //fill dhtmlxwindow with proper content
        else if (id==="window_b") var x = wins.b({x:1}); //fill dhtmlxwindow with proper content
        else if (id==="window_c") var x = wins.c({x:1}); //fill dhtmlxwindow with proper content
        //and so on for literally thousands of items.
    }
};

window.wins = {
    a: function(args) {
        //this.myName = 'wins.a'; is used for the help topic.
        //DB contains columns: [item] / [helpurl]
        //Example Data: [wins.a] / [/help/gettingstarted.html]
        //That is why in this previous post (http://stackoverflow.com/q/28096922/3112803)
        //I was wanting to know if a function could know it's own name so I wouldn't
        //have to type this line below for 1000s of items.
        this.myName = 'wins.a';
        console.log('Window-A is now displayed. Use "'+this.myName+'" to make link to help topic.');
    },
    b: function(args) {
        this.myName = 'wins.b';
        console.log('Window-B is now displayed. Use "'+this.myName+'" to make link to help topic.');
    },
    c: function(args) {
        this.myName = 'wins.c';
        console.log('Window-C is now displayed. Use "'+this.myName+'" to make link to help topic.');
    }
};

回答1:

Another approach would be to re-write the current usage of accessing object properties via the dot notation and use the bracket notation instead.

launch_no_eval:function(id) {
        //we init a blank dhtmlxwindow and do some other things here, then...
        if (id==="window_a") var x = wins.a({x:1}); //fill dhtmlxwindow with proper content
        else if (id==="window_b") var x = wins.b({x:1}); //fill dhtmlxwindow with proper content
        else if (id==="window_c") var x = wins.c({x:1}); //fill dhtmlxwindow with proper content
        //and so on for literally thousands of items.
    }

could be re-written as follows,

launch_no_eval:function(id) { 
        var x = wins[id]({x:1});
}

This would mean your HTML markup can change from,

<a href="javascript:core.launch_no_eval('window_a');">Window-A</a><br>
<a href="javascript:core.launch_no_eval('window_b');">Window-B</a><br>
<a href="javascript:core.launch_no_eval('window_c');">Window-C</a><br><br>

to,

<a href="javascript:core.launch_no_eval('a');">Window-A</a><br>
<a href="javascript:core.launch_no_eval('b');">Window-B</a><br>
<a href="javascript:core.launch_no_eval('c');">Window-C</a><br><br>

As Daniel commented below, assuming you have no control over the HTML markup and must use the window_# value being passed in then you could perform the following,

launch_no_eval:function(id) {
        // replace 'window_' with empty string to retrieve unique id
        var x = wins[id.replace('window_', '')]({x:1});
}

来源：https://stackoverflow.com/questions/28098239/eval-vs-if-statements-many-if-statements