mathjs/lib/type/boolean.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

'use strict';

var deepMap = require('./../utils/collection/deepMap');

function factory(type, config, load, typed) {
  /**
   * Create a boolean or convert a string or number to a boolean.
   * In case of a number, `true` is returned for non-zero numbers, and `false` in
   * case of zero.
   * Strings can be `'true'` or `'false'`, or can contain a number.
   * When value is a matrix, all elements will be converted to boolean.
   *
   * Syntax:
   *
   *    math.boolean(x)
   *
   * Examples:
   *
   *    math.boolean(0)     // returns false
   *    math.boolean(1)     // returns true
   *    math.boolean(-3)     // returns true
   *    math.boolean('true')     // returns true
   *    math.boolean('false')     // returns false
   *    math.boolean([1, 0, 1, 1])     // returns [true, false, true, true]
   *
   * See also:
   *
   *    bignumber, complex, index, matrix, string, unit
   *
   * @param {string | number | boolean | Array | Matrix | null} value  A value of any type
   * @return {boolean | Array | Matrix} The boolean value
   */
  var bool = typed('bool', {
    '': function _() {
      return false;
    },
    'boolean': function boolean(x) {
      return x;
    },
    'number': function number(x) {
      return !!x;
    },
    'null': function _null(x) {
      return false;
    },
    'BigNumber': function BigNumber(x) {
      return !x.isZero();
    },
    'string': function string(x) {
      // try case insensitive
      var lcase = x.toLowerCase();

      if (lcase === 'true') {
        return true;
      } else if (lcase === 'false') {
        return false;
      } // test whether value is a valid number


      var num = Number(x);

      if (x !== '' && !isNaN(num)) {
        return !!num;
      }

      throw new Error('Cannot convert "' + x + '" to a boolean');
    },
    'Array | Matrix': function ArrayMatrix(x) {
      return deepMap(x, bool);
    }
  });
  return bool;
}

exports.name = 'boolean';
exports.factory = factory;