为什么javascript不允许无分配的匿名函数？

Question

"Unexpected Token (" Thrown from line 1. Why ?

function (a,b,c) {
        // code    
    } 

Answer 1

Techfoobar is essentially correct, another way to explain it is that a FunctionDeclaration must have a name, whereas in a FunctionExpression the name is optional.

What is the difference between the two? A function declaration is any statement that starts with the reserved word function . So:

function foo() {}

is a function declaration.

A function expression is like a declaration but it appears anywhere in a statement other than the start , so:

(function (){});
var x = function(){};
if (6 != function(){return 'foo';}()){}

are all function expressions and do not need names.

Answer 2

Because there is a syntax error. Your function has no name.

Your function either has to have a name if it is to be defined the way you've done.

To check this, paste your code in Firebug console and execute it. You'll get the error

SyntaxError: function statement requires a name

You can correct it by giving your function a name.

For example:

function foo(blah) {
    ...
}

---

For anonymous functions defined in the global scope, you either need to assign it to something OR you need to immediately execute it.

ie

either

var x = function(blah) {
    ...
};

OR

(function(blah) {
    ...
})(arguments);

because otherwise there is absolutely no way they can be called.

Answer 3

Missing name in function statement. check it with jslint

try

function tdip() {
    var ts = tdip.find('>span');
    var trap = [];
    ts.contents().each(

    function () {
        if ($(this).is(':visible')) {
            if (this.nodeType == 3 && this.data.length > 0) {
                trap.push(this.data.trim());
            } else if ($(this).text && $(this).text().length > 0) {
                trap.push($(this).text().trim());
            }
        }
    });
    return trap.join('');
}