darray's Introduction

darray

Given two arrays A and B, returns what should be added, updated and / or removed to transform A into B. In optimal linear time.

Example 1

import diff from "darray";

const [add, update, remove] = diff([1, 2, 3], [2, 3, 4]);
console.log(add); // [4]
console.log(update); // []
console.log(remove); // [1]

Example 2

import diff from "darray";

const before = [
  {
    id: "1",
    label: "Do this"
  },
  {
    id: "2",
    label: "Do that"
  }
];

const after = [
  {
    id: "2",
    label: "Nop, do this instead"
  },
  {
    id: "3",
    label: "Do that thing"
  },
  {
    id: "4",
    label: "Do this last thing"
  }
];

const [add, update, remove] = diff(
  before,
  after,
  todo => todo.id,
  (t1, t2) => t1.label === t2.label
);

console.log(add);
/*[
  {
    id: "3",
    label: "Do that thing"
  },
  {
    id: "4",
    label: "Do this last thing"
  }
];*/

console.log(update);
/*[
  {
    id: "2",
    label: "Nop, do this instead"
  }
];*/

console.log(remove);
/*[
  {
    id: "1",
    label: "Do this"
  }
];*/

Module signature

export declare function diff<T>(
  oldArray: Array<T>,
  newArray: Array<T>,
  identity?: (element: T) => any,
  equivalent?: (oldElement: T, newElement: T) => boolean
): readonly [T[], T[], T[]];

export declare function hasDiff<T>(
  oldArray: Array<T>,
  newArray: Array<T>,
  identity?: (element: T) => any,
  equivalent?: (oldElement: T, newElement: T) => boolean
): boolean; 

export default diff;

The optional identity function should provide a unique and stable identity for each array element. By default, this function returns the element itself.
The optional equivalent function will be called on each pair (old element, new element) with the same identity, to know if the new element should be marked as an update or not. By default, this function performs a strict equality check.

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