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I was browsing the JIT's code, and I saw this:
var isGraph = ($type(json) == 'array');
var ans = new Graph(this.graphOptions);
if(!isGraph)
//make tree
(function (ans, json) {
ans.addNode(json);
for(var i=0, ch = json.children; i<ch.length; i++) {
ans.addAdjacence(json, ch[i]);
arguments.callee(ans, ch[i]);
}
})(ans, json);
else
//make graph
(function (ans, json) {
var getNode = function(id) {
for(var w=0; w<json.length; w++) {
if(json[w].id == id) {
return json[w];
}
}
return undefined;
};
What could be the purpose for those anonymous functions? They immediately pass out of scope, right?
Why use:
(function (ans, json) {
ans.addNode(json);
for(var i=0, ch = json.children; i<ch.length; i++) {
ans.addAdjacence(json, ch[i]);
arguments.callee(ans, ch[i]);
}
})(ans, json);
instead of:
ans.addNode(json);
for(var i=0, ch = json.children; i<ch.length; i++) {
ans.addAdjacence(json, ch[i]);
arguments.callee(ans, ch[i]);
}
Is this some super elite JS hack?
528
An anonymous function is not accessible after its initial creation, it can only be accessed by a variable it is stored in as a function as a value. 3. This function is useful for all scenarios. An anonymous function can be useful for creating IIFE(Immediately Invoked Function Expression).
An anonymous function is a function that is not stored in a program file, but is associated with a variable whose data type is function_handle . Anonymous functions can accept multiple inputs and return one output. They can contain only a single executable statement.
An anonymous function is a function which doesn't contain any name. It is useful when you want to create an inline function. In Go language, an anonymous function can form a closure. An anonymous function is also known as function literal.
Anonymous functions are often arguments being passed to higher-order functions, or used for constructing the result of a higher-order function that needs to return a function. If the function is only used once, or a limited number of times, an anonymous function may be syntactically lighter than using a named function.
They just want to implement recursion in that small piece of code:
(function (ans, json) {
ans.addNode(json);
for(var i=0, ch = json.children; i<ch.length; i++) {
ans.addAdjacence(json, ch[i]);
arguments.callee(ans, ch[i]); // <-- recursion!
}
})(ans, json);
The arguments.callee property refers to the currently executing function, if you remove the anonymous function, it will refer to the enclosing function, and I don't think they want to invoke the whole function again.
102
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