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4.6: higher order functions, callbacks and this - Coggle Diagram

- - - - taking them as arguments, or
      - returning them
- - - - globals
        
        var firstName = "James", lastName = "West";
      - object
        
        var user = { firstName: "Cory", lastName: "Sikahema", fullName: function() { setTimeout(function() { console.log(this.firstName + " " + this.lastName) }, 2000) } };
      - use the method as a callback
        
        user.fullName()
        
        outputs
        
        > James West
        
        :explode: we have lost the value of this
        
        so the global values are used
    - - to create a new function
        
        with this bound to an object
      - var user = { firstName: "Cory", lastName: "Sikahema", fullName: function() { setTimeout(function() { console.log(this.firstName + " " + this.lastName); }.bind(this), 2000) } };
      - outputs
        
        > Cory Sikahema
- - - - when we use callbacks
    - - var sum = function(num1, num2) { return num1 + num2: };
      - as an arrow funtion
        
        var sum = (num1, num2) => num1 + num2;
    - - :!:must be
        
        function expressions
      - :warning: cannot be
        
        function declarations
        
        are always anonymous
  - - - this
      - arguments
      - super
    - - constructors
        
        calling with new throws a TypeError
    - - methods
        
        this will be undefined
        
        :!!:but can be used within methods
        
        will inherit the this bound to the method
  - - - var user = { firstName: "Cory", lastName: "Sikahema", fullName: function() { setTimeout(() => { console.log(this.firstName + " " + this.lastName); }, 2000) } };
      - outputs
        
        > Cory Sikahema