a = function (){
var b = 10;
var k = function(){
console.log(b);
}();
}();
The above code will print 10.
var k = function(){
console.log(b);
}
var a = function (){
var b = 10;
k();
}();
This code will print undefined.
Is it possible to print 10 instead? Like binding the scope to k before calling it.
As @Derek answered, you can obviously pass an argument.
Aside from that, you can't transfer or change variable scope, but you can directly manipulate calling context.
As such, you can set b as the property of an object, and set that object as the calling context of whatever function you're calling.
var k = function(){
console.log(this.b);
}
var a = function (){
var obj = {b:10};
k.call(obj);
}();
The .call() method invokes the k function, but sets the first argument you provide as the calling context of the called function.
In fact, you don't technically need to use an object. You could directly set the number as the value to use...
var k = function(){
console.log(this);
}
var a = function (){
var b = 10;
k.call(b);
}();
In strict mode, you'll get the number, but in non-strict, you'll get the Number as its object wrapper.
exports, and then returns the exports object. So you need to imagine some hidden code above and below your module code. The whole code is invoked the first time your module is requested via require. The returned exports object is cached in an internal Array, so that future requests to the same module don't need to run your code again, but instead just get your exports object from the Array. If you need I can show a simplified example of what they do.var app = require('express').createServer(), what is happening is that the require function grabs the express module code, wraps it in more code, evals it, stores the returned object, and delivers that object to you. So it's ultimately just the same as calling a function that returns an object, and putting that object in your app variable. There's no shared scope.Really? What have you tried?
var k = function(b){
console.log(b);
}
var a = function (){
var b = 10;
k(b); //Done.
}();
Why does it give you undefined in your second example is because b is not defined. You have to define it first before using the variable b.
var k = function(b){ //<--There, defined. Mission accomplished.
Access into the scope can be granted through eval.
var a = (function() {
var b = 10;
return {
eval: function(s) {
return eval(s);
}
};
})();
var k = function() {
console.log(a.eval("b"));
};
k();
