Question

if I have this json structure:

var j = {
    param1: 'hello',
    param2: 'world',
    func:   function() {
        console.log(this.param1 + ' ' + this.param2);
    }
};

this in func is undefined. How to access self in this json object? Thanks

EDIT:

I’m trying it with:

j.func();

Answer 1

this is determined by how a function is called. To answer your question, we would need to see how you are called func().

If you call:

j.func()

then, this inside of func will be set to j.

If you call func() directly (which is what happens if you pass j.func as a callback which is then called directly by some other function), then this will probably be set to either window or undefined depending upon whether you are in strict mode or not. For example:

function callme(callback) {
    // the context of `j` will be lost here and 
    // this will just call func() directly without setting this to j
    callback();
}

callme(j.func);

this can also be set explicitly by the caller by using j.func.apply() or j.func.call() which allow the caller to specify the desired value of this.