assertArrays.js

const doesContain = function(array, element) {
  return array.indexOf(element) !== -1;
};

const doesContainAll = function(array, values) {
  return values.every((element) => doesContain(array, element));
};

const doesContainAny = function(array, values) {
  return values.some((element) => doesContain(array, element));
};

const compare = function(actual, expected) {
  return actual.length === expected.length && actual.every((value, index) => value === expected[index]);
};

const isSorted = function(array, fn) {
  return compare(array, array.slice().sort(fn));
};

module.exports = (chai) => {

  chai.Assertion.addMethod('containing', function(value) {
    this.assert(
      doesContain(this._obj, value),
      `expected #{this} to be containing ${value}`,
      `expected #{this} not to be containing ${value}`
    );
  });

  chai.Assertion.addMethod('containingAllOf', function(values) {
    this.assert(
      doesContainAll(this._obj, values),
      `expected #{this} to be containing all of [${values}]`,
      `expected #{this} not to be containing all of [${values}]`
    );
  });

  chai.Assertion.addMethod('containingAnyOf', function(values) {
    this.assert(
      doesContainAny(this._obj, values),
      `expected #{this} to be containing any of [${values}]`,
      `expected #{this} not to be containing any of [${values}]`
    );
  });

  chai.Assertion.addMethod('equalTo', function(values) {
    this.assert(
      compare(this._obj, values),
      `expected #{this} to be equal to [${values}]`,
      `expected #{this} not to be equal to [${values}]`
    );
  });

  chai.Assertion.addMethod('ofSize', function(length) {
    this.assert(
      this._obj.length === length,
      `expected #{this} to be of size ${length}`,
      `expected #{this} not to be of size ${length}`
    );
  });

  chai.Assertion.addMethod('array', function() {
    this.assert(
      this._obj instanceof Array,
      'expected #{this} to be an Array',
      'expected #{this} not to be an Array'
    );
  });

  chai.Assertion.addMethod('Uint8Array', function() {
    this.assert(
      this._obj instanceof Uint8Array,
      'expected #{this} to be an Uint8Array',
      'expected #{this} not to be an Uint8Array'
    );
  });

  chai.Assertion.addMethod('Uint16Array', function() {
    this.assert(
      this._obj instanceof Uint16Array,
      'expected #{this} to be an Uint16Array',
      'expected #{this} not to be an Uint16Array'
    );
  });

  chai.Assertion.addMethod('Uint32Array', function() {
    this.assert(
      this._obj instanceof Uint32Array,
      'expected #{this} to be an Uint32Array',
      'expected #{this} not to be an Uint32Array'
    );
  });

  chai.Assertion.addMethod('Uint8ClampedArray', function() {
    this.assert(
      this._obj instanceof Uint8ClampedArray,
      'expected #{this} to be an Uint8ClampedArray',
      'expected #{this} not to be an Uint8ClampedArray'
    );
  });

  chai.Assertion.addMethod('sorted', function(sortfn) {
    this.assert(
      isSorted(this._obj, sortfn),
      'expected #{this} to be sorted',
      'expected #{this} not to be sorted'
    );
  });

};