Methods

In JavaScript methods are object properties containing a function definition. Within the function definition, this can be used to refer to the containing object as long as the function is defined within the object.

Note: If a function is assigned to a property later, any reference to this will reflect the context of the new function. Also, if the object’s function is assigned to a variable and executed via the variable, this will reflect the variable’s execution context.

Syntax

A method of an object is called via the following syntax:

objectName.methodName();

If a method is called without parenthesis, it is being called as a property, which means it will return the function definition, not execute the method.

Example

const car = {
  make: 'Honda',
  model: 'Civic',
  year: 2019,
  printOut: function () {
    console.log(this.year + ' ' + this.make + ' ' + this.model);
  },
};

car.printOut();
// Output: 2019 Honda Civic

// Referenced as a property
var method = car.printOut;

car.year = 2020;

method();
// Output: undefined undefined undefined;
// 'this' is being referenced outside an object context
// can be fixed by explicitly setting the object context with 'bind()'

method = car.printOut.bind(car);

method();
// Output: 2020 Honda Civic