函数内部的访问参数名称字符串

Question

Is it possible to access arguments name strings?!

function myFunction (a, b, c, d, e, f) {
    var obj = [];
    [].forEach.call(arguments, function(arg) {
        obj.push({
            // question is how to get variable name here?
            name: "a",// "a", "b", "c", "d", "e", "f"
            value: arg, //a, b, c, ,d, e, f
        })
    });
 return obj;
}

myFunction(1,2,3,4,5,6); // return [{name: "a", value: 1}, {name: "b", value: 2}...]

Note: I know using arguments is not a good practice. I want to know if this even possible or not?

Answer 1

You could try something like this:

function myFunction (a, blabla, c, somethingElse, e, f) {
    var obj = [];
    //'(a, b, c, d, e, f)' 
    var tmp = arguments.callee.toString().match(/\(.*?\)/)[0];
    //["a", "b", "c", "d", "e", "f"] 
    var argumentNames = tmp.replace(/[()\s]/g,'').split(',');

    [].splice.call(arguments,0).forEach(function(arg,i) {
        obj.push({
            // question is how to get variable name here?
            name: argumentNames[i],
            value: arg
        })
    });
    return obj;
}

console.log(JSON.stringify(myFunction(1, 2, 3, 4, 5, 6)));
//Output-> [{"name":"a","value":1},{"name":"blabla","value":2},
//          {"name":"c","value":3},{"name":"somethingElse","value":4},
//          {"name":"e","value":5},{"name":"f","value":6}]

DEMO

Answer 2

Are the function parameter names definied in the function definition, as you've written above? If so, you can just create an array in the function:

function myFunction(a,b,c,d,e,f) {
  var argNames = ['a','b','c','d','e','f'];
  ...
}

arguments will only ever contain a simple array of the arguments passed to the function. There is no default mapping from arguments to parameter names. That I'm aware of anyway

Answer 3

This works:

function myFunction( _obj ) {

    var obj = [],
        names = [],
        args = arguments,
        len = function(o) {
            var a = [];

            for (var i in o) a.push(i);

            return a;
        };

    for (var i in _obj) names.push( i );

    [].forEach.call( len(_obj), function(a, b) {
        obj.push({
            name: names[b],
            value: args[0][names[b]]
        });
    });

    return obj;

}

console.log( myFunction({
    a: 1,
    b: 2,
    c: 3,
    d: 4,
    e: 5,
    f: 6
}));​​​​

Here is a DEMO

Answer 4

For completeness: you can't use named parameters in javascript. If you want to use them (and thus be able to identify the parameter names), a workaround is to supply an object:

function myParams(params){
  var ret = [];
  for (var l in params){ 
   if (params.hasOwnProperty(l)){
    ret.push(l);
   }
  }
  return ret
}
myParams({a:1,b:2,c:3,d:null,e:null,f:null,g:11});
//=> [a,b,c,d,e,f,g]

See also...
And to be really complete: see this also

Answer 5

You can invoke toString on the function and then use some kind of RegEx to parse result.

    function someFunction(a,b,c){}
    var functionString = someFunction.toString(); //return "function someFunction(a,b,c){}"
    var args = functionString.match(/^function (?:.*?)\((.*?)\)/);
    if(args[1])
    {
        var argsNames = args[1].split(",");
    }

I've tested it on FF and Chrome.

Answer 6

Since item.product_image2 is a URL string, you need to put it in quotes when you call changeImage inside parameter.

My Function Onclick

items+='<img src='+item.product_image1+' id="saleDetailDivGetImg">';
items+="<img src="+item.product_image2+"  onclick='changeImage(\""+item.product_image2+"\");'>";

My Function

<script type="text/javascript">
function changeImage(img)
 {
    document.getElementById("saleDetailDivGetImg").src=img;
    alert(img);
}
</script>