mathjs/lib/esm/function/matrix/filter.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

import { optimizeCallback } from '../../utils/optimizeCallback.js';
import { filter, filterRegExp } from '../../utils/array.js';
import { factory } from '../../utils/factory.js';
var name = 'filter';
var dependencies = ['typed'];
export var createFilter = /* #__PURE__ */factory(name, dependencies, _ref => {
  var {
    typed
  } = _ref;
  /**
   * Filter the items in an array or one dimensional matrix.
   *
   * The callback is invoked with three arguments: the current value,
   * the current index, and the matrix operated upon.
   * Note that because the matrix/array might be
   * multidimensional, the "index" argument is always an array of numbers giving
   * the index in each dimension. This is true even for vectors: the "index"
   * argument is an array of length 1, rather than simply a number.
   *
   * Syntax:
   *
   *    math.filter(x, test)
   *
   * Examples:
   *
   *    function isPositive (x) {
   *      return x > 0
   *    }
   *    math.filter([6, -2, -1, 4, 3], isPositive) // returns [6, 4, 3]
   *
   *    math.filter(["23", "foo", "100", "55", "bar"], /[0-9]+/) // returns ["23", "100", "55"]
   *
   * See also:
   *
   *    forEach, map, sort
   *
   * @param {Matrix | Array} x    A one dimensional matrix or array to filter
   * @param {Function | RegExp} test
   *        A function or regular expression to test items.
   *        All entries for which `test` returns true are returned.
   *        When `test` is a function, it is invoked with three parameters:
   *        the value of the element, the index of the element, and the
   *        matrix/array being traversed. The function must return a boolean.
   * @return {Matrix | Array} Returns the filtered matrix.
   */
  return typed('filter', {
    'Array, function': _filterCallback,
    'Matrix, function': function Matrix_function(x, test) {
      return x.create(_filterCallback(x.valueOf(), test), x.datatype());
    },
    'Array, RegExp': filterRegExp,
    'Matrix, RegExp': function Matrix_RegExp(x, test) {
      return x.create(filterRegExp(x.valueOf(), test), x.datatype());
    }
  });
});

/**
 * Filter values in a callback given a callback function
 * @param {Array} x
 * @param {Function} callback
 * @return {Array} Returns the filtered array
 * @private
 */
function _filterCallback(x, callback) {
  var fastCallback = optimizeCallback(callback, x, 'filter');
  return filter(x, function (value, index, array) {
    // invoke the callback function with the right number of arguments
    return fastCallback(value, [index], array);
  });
}