First, See my code plz.
function test(){
this.item = 'string';
this.exec = function(){
something();
}
function something(){
console.log(this.item);
console.log('string');
}
}
And I made class and call 'exec function', like this code
var t = new test();
t.exec();
But result is...
undefined
string
I wanna access from something function to test.item.
Have you any solution?
You need to call something with apply so that this is properly set inside of something:
function test(){
this.item = 'string';
this.exec = function(){
something.apply(this);
}
function something(){
console.log(this.item);
console.log('string');
}
}
As @aaronfay pointed out, this happens because this doesn't refer to the object that new test() created. You can read more about it here, but the general rule is:
If a function is invoked on an object, then this refers to that object. If a function is invoked on its own (as is the case in your code), then this refers to the global object, which in the browser is window.
function something() {} alters the context of the this keyword, and that's why it's no longer as expected. apply effectively "applies" the context of this to another function.You have many choices, but I recommend the last one.
var item = 'string'
or
this.exec = function(){
something.apply(this, []);
}
or
var that = this;
function something(){
console.log(that.item);
console.log('string');
}
this.item in something() isn't what you think it is.
The this value is different. In this case, it's the global object.
The best solution, in my opinion, is to declare a variable with a reference to this, that can be accessed inside the inner function.
function test() {
var that = this; // a reference to 'this'
function something() {
console.log(that.item); // using the outer 'this'
console.log('string');
}
this.item = 'string';
this.exec = function(){
something();
}
}
var that = this; is much more dynamic and easy to type in big applications. I'm the creator of a JS library similar to jQuery, so I know that.Why not just define something like this:
function test(){
this.item = 'string';
this.exec = function(){
this.something();
}
this.something = function(){
console.log(this.item);
console.log('string');
}
}
var t = new test();
t.exec();
// output:
// string
// string
