"method overload" in javascript

Question

So, I admit that I am new to javascript and that I came from C. + background ("Hello, I am Bob, I am a class-based static user", chorus of "Hello, Bob!".).

I find that I often get features like:

function someFunc()
{
    if (arguments.length === 0 ){
       ...
    } else {
       ...
    }
}

(where there may be three such cases). Or else, I write the difference in the name:

function someFuncDefault() { ... };
function someFuncRealArg(theArg) { ... };

(Replace “RealArg” for some semantically-filled phrase).

Is there a better sample for this kind of thing?

Answer 1

Check out this post .

Answer 2

I don’t know that I would do it like this, but it looks like it could make your code softer less unmanageable:

function someFunc() {
    switch (arguments.length) {
        case 0: noArgs();
        case 1: oneArg(arguments[0]);
        case 2: twoArgs(arguments[0], arguments[1]);
    }
    function noArgs() {
        // ...
    }
    function oneArg(a) {
        // ...
    }
    function twoArgs(a, b) {
        // ...
    }
}

:

function someFunc(a, b) {
    if ('string' == typeof a) {
        // ...
    } else if ('number' == typeof a) {
        // ...
    }
}

, , , , , ( , ).

Answer 3

Javascript .

- :

( , , "" ):

function bar(arg1, arg2) {
  if(arg1 === undefined) { set default }
  if(arg2 === undefined) { set default }
  //do stuff here
}

, false:

function foo(arg1, arg2) {
  if(!arg1) { set default }
  if(!arg2) { set default }
  //do stuff here
}

javascript - Douglas Crockford javascript: http://video.yahoo.com/search/?p=javascript

Answer 4

, no?

Javascript , . - . param, .

? , , , arg1 arg2, , , .

function someFunc(params)
{
  var x = params.x || defaultX;
  var y = params.y || defaultY;

  //businesslogic
}

someFunc({x:'foo',y:'bar'});

someFunc({y:'baz'});

Answer 5

Javascript ( , Python, ).

function someFunc(arg1, arg2)
{
  if(typeof(arg1) == "undefined") {
    arg1 = default;
  }
  ... 
}

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Answer 6

, , , JavaScript , .

JavaScript , :

function foo(bar, baz) {
    bar = bar || defaultBar;
    baz = baz || defaultBaz;
    .
    .
    .
}

Answer 7

, , , , .

//concat(str1, str2 [,str3 [,str4 [,str5]]])
function concat(str1, str2, str3, str4, str5) {
    var str = str1 + str2;
    if(str3 != undefined)
        str += str3;
    if(str4 != undefined)
        str += str4;
    if(str5 != undefined)
        str += str5;
    return str;
}

, , (.. str3 str5, str4).

//concat({str1:string, str2:string, str3:string, str4:string, str5:string})
//str3, str4, and str5 are optional
function concat(strngs) {
    var str = strngs.str1 + strngs.str2;
    if(strngs.str3 != undefined)
        str += strngs.str3;
    if(strngs.str4 != undefined)
        str += strngs.str4;
    if(strngs.str5 != undefined)
        str += strngs.str5;
    return str;
}

Answer 8

bob.js:

var notify = new bob.fn.overloadFunction([ 
    { 
        condition: function(msg) { return bob.utils.isString(msg); }, 
        overload: function(msg) { 
            console.log(msg); 
        } 
    }, 
    { 
        condition: function(bSayHello) { return bob.utils.isBoolean(bSayHello); }, 
        overload: function(bSayHello, msg) { 
            msg = bSayHello ? 'Hello: ' + msg : msg; 
            console.log(msg); 
        } 
    } 
]); 

:

notify('Simple sentence.'); 
// Output: 
// Simple sentence. 
notify(true, 'Greeting sentence.'); 
// Output: 
// Hello: Greeting sentence. 
notify(123); 
// JavaScript Error: 
// "No matching overload found."