I want to have a function A that accepts another function B as an argument, and then runs B as it were defined within the closure scope of A, ie has access to all the local variables.
For example, simplistically:
var A = function(B){
var localC = "hi";
B();
}
var B = function(){
console.log(localC);
}
A(B); // to log 'hi'
The only way I have found is to use eval. Does ec6 give any better options maybe?
One solution is to pass localC
as argument in function B
:
var A = function(B) { var localC = "hi"; B(localC); } var B = function(localC) { console.log(localC); } A(B); // outputs hi
Alternative using arguments
:
var A = function(B) { var localC = "hi"; B(localC, "test"); } var B = function() { var i = 0; for (i; i < arguments.length; i++) { console.log(arguments[i]); } } A(B); // outputs hi, test
var A = function(B){ var self = this; self.localC = "hi"; self.localD = "hello"; B(); }; var B = function(){ var self=this; alert(self.localD); } A(B); // to log 'hi'
You can make the context explicit and pass it to B
:
var A = function(B){
var context = {
localC: "hi"
};
B(context);
}
var B = function(context){
console.log(context.localC);
}
A(B); // hi
You can also use this
with new
and prototype
:
var A = function() {
this.localC = "hi";
}
A.prototype.b = function(context){
console.log(this.localC);
}
var a = new A();
a.b(); // hi
or without the prototype
:
var A = function() {
this.localC = "hi";
}
var a = new A();
a.b = function(context){
console.log(this.localC);
};
a.b(); // hi
You can use this
with bind
:
var a = {
localC: "hi"
};
function B(foo) {
console.log(this.localC, foo);
}
B.bind(a)("foo"); // hi foo
// .call:
B.call(a, "foo"); // hi foo
bind
sets the context for this
. call
takes the context as it's first argument.
This one is not good:
var A = function(B){
var localC = "hi";
B.bind(this)(); // this is the global object, you need `new` to create a new scope
}
var B = function(){
console.log(this.localC);
}
A(B); // undefined
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.