diff

external fun diff(actual: String, expected: String): ReadonlyArray<DiffEntry>(source)

external fun diff(actual: String, expected: ReadonlyArray<String>): ReadonlyArray<DiffEntry>(source)

external fun diff(actual: ReadonlyArray<String>, expected: String): ReadonlyArray<DiffEntry>(source)

external fun diff(actual: ReadonlyArray<String>, expected: ReadonlyArray<String>): ReadonlyArray<DiffEntry>(source)

util.diff() compares two string or array values and returns an array of difference entries. It uses the Myers diff algorithm to compute minimal differences, which is the same algorithm used internally by assertion error messages.

If the values are equal, an empty array is returned.

const { diff } = require('node:util');

// Comparing strings
const actualString = '12345678';
const expectedString = '12!!5!7!';
console.log(diff(actualString, expectedString));
// [
//   [0, '1'],
//   [0, '2'],
//   [1, '3'],
//   [1, '4'],
//   [-1, '!'],
//   [-1, '!'],
//   [0, '5'],
//   [1, '6'],
//   [-1, '!'],
//   [0, '7'],
//   [1, '8'],
//   [-1, '!'],
// ]
// Comparing arrays
const actualArray = ['1', '2', '3'];
const expectedArray = ['1', '3', '4'];
console.log(diff(actualArray, expectedArray));
// [
//   [0, '1'],
//   [1, '2'],
//   [0, '3'],
//   [-1, '4'],
// ]
// Equal values return empty array
console.log(diff('same', 'same'));
// []

Since

v22.15.0

Parameters

actual

The first value to compare

expected

The second value to compare