Steps:
1. Create qt quick application(build-in element).
2. Add a js file to the project.
3. add some code like

function Vector(x, y)
{
this.x = x;
this.y = y;

this.getX = function()

}

var v = new Vector(1,1);
var x = v.getX();

4. select getX() or v, right click the mouse to choose "Follow Symbol
Under Cursor". Does not work.
5. Only work for "new Vector(1,1)", so if supply "Follow Symbol Under Cursor"
for variable and function name will be more convenient for js programming.