[Javascript] Combine Objects with Object.assign and Lodash merge

Learn how to use Object.assign to combine multiple objects together. This pattern is helpful when writing libraries that have a set of default options where you want to allow a user to override specific options. You'll also learn how to use a third party library to recursively merge nested objects together.

const defaultOptions = {
  amount: 10,
  quantity: 1,
  color: 'maroon',
  material: 'cotton',
  sizes: {
    small: true,
    medium: true,
    large: true
  }
};

function inventory(userOptions) {
  console.log(Object.assign({}, defaultOptions, userOptions));
  /*
  [object Object] {
  amount: 15,
  color: "maroon",
  material: "wool",
  quantity: 6,
  sizes: [object Object] {
    extraLarge: true
  }
}
  */
  console.log(_.merge({}, defaultOptions, userOptions));
  /*
  [object Object] {
  amount: 15,
  color: "maroon",
  material: "wool",
  quantity: 6,
  sizes: [object Object] {
    extraLarge: true,
    large: true,
    medium: true,
    small: true
  }
}
  */
};

inventory({
  amount: 15,
  quantity: 6,
  material: 'wool',
  sizes: {
    extraLarge: true
  }
});