cal-rule

cal-rule

A simple javascript/typescript calculating rule solution.

1A&2B|!(3C&4D)

operator & | ! () are supported.

select and input are supported.

• 1A means choose the first item of first choice;
• 1 means first value is valid;
• 1B&2A means choose second option of first question and first options of second question.
• 1B|2A means choose second option of first question or first options of second question.
• ! means reverse, if 1A parsed to true, !1A will parsed to false.
• You can customize your own strategy as well;

install

npm install cal-rule

yarn add cal-rule

pnpm add cal-rule

usage

init

import { init } from 'cal-rule';

const ruleStr = '1A&2B';

const rule = init(ruleStr);

While using typescript, you can also appoint the value type of rule.

const rule = init<string>(ruleStr);

if ruleStr is invalid, init will throw a Error;

choices & values & parse

cal-rule requires choices and values to calculate, choices[0][0] will be considered as 1A.

const rule = init(ruleStr);

const choices = [
  ['option1A', 'option1B', 'option1C'],
  ['option2A', 'option2B', 'option2C', 'option2D'],
  ['option3A', 'option3B']
];

const values = ['option1A', 'option2B', undefined];

// since the ruleStr only infer to the value of position [0] and [1], choices[2] and values[2] will be ignored.
rule.choices = choices;
rule.values = values;

// true
const ans: boolean = rule.parse();

If there is a input value instead of select, which means no choices can be provided, undefined is ok to be passed as an item of choices.

const ruleStr = '1A&2';

const rule = init(ruleStr);

const choices = [['option1A', 'option1B', 'option1C'], undefined, ['option3A', 'option3B']];

const values = ['option1A; option1B; option1C', 'input value', undefined];

rule.choices = choices;
rule.values = values;

// true
const ans: boolean = rule.parse();

parse provide a functional param to cover the default calculator;

const choices = [
  ['option1A', 'option1B', 'option1C'],
  ['option2A', 'option2B', 'option2C', 'option2D'],
  ['option3A', 'option3B']
];

const values = ['option1A; option1B; option1C', 'option2B; option2D', undefined];

rule.choices = choices;
rule.values = values;

// true
const ans: boolean = rule.parse((value, choice): boolean => {
  if (value) {
    return value.includes(choice);
  }
  return false;
});

The second param choice is defined by ruleStr and choices. 1A means choices[0][0], while 2B means choices[1][1]

In 1A&2B case:

serial	value	choice	rule	ans
0	'option1A; option1B; option1C'	'option1A'	1A	true
1	'option2B; option2D'	'option2B'	2B	true
2	values	choices	1A&2B	ans[0] & ans[1] === true

Default function pass to parse ↓

const defaultCalculator = <Choice = any, Value = Choice>(
  value: Value | undefined,
  choice: Choice | undefined
): boolean => {
  if (typeof value === 'undefined' || value === null) {
    return false;
  }
  if (typeof choice !== 'undefined') {
    if (typeof value === typeof choice) {
      return (value as unknown) === (choice as unknown);
    }
    if (value instanceof Array) {
      return value.includes(choice);
    } else {
      if (config.warning) {
        console.warn(
          'Default calculator cannot handle this type of value and choice, please define your own calculator by calRule.calculator'
        );
      }
      throw new CalRuleRequiredError('calculator');
    }
  } else {
    if (typeof value === 'string') {
      return value.trim().length > 0;
    }
    return true;
  }
};

calculator

cal-rule allows developer to customize the default calculator.

rule.calculator = (value, choice): boolean => {
  if (value) {
    return value.includes(choice);
  }
  return false;
};

other

cal-rule can check extra choice that is not includes in choices but checked by rule.

const rule: CalRule = init('1E');
const choices = [['A', 'B', 'C', 'D']];
it('other option', () => {
  rule.choices = choices;
  rule.values = ['other'];
  // return false
  rule.parse();
});

1E infer to choices[0][4], which does not exist, so parse should return a false.

However, sometimes you may have extra value that is not included in choices

const definedChoices = ['OptionA', 'OptionB', 'OptionC', 'OptionD'];
const realChoices = ['OptionA', 'OptionB', 'OptionC', 'OptionD', 'Custom Input Value: Other'];

rule.choices = definedChoices;

cal-rule can regard such extra value as a other choice.

/** set config other true */
const rule: CalRule = init('1E', {
  other: true
});
const choices = [['A', 'B', 'C', 'D']];
it('other option', () => {
  rule.choices = choices;
  rule.values = ['other'];
  // return true
  rule.parse();
});

because of 1E meaning choices[0][4] and 4 === choices[0].length + 1, cal-rule will check if value[0] is a valid extra value.

inValid extra value: '', NaN, undefined, null, [].

rule 1E exactly responses to choices[0].length + 1; in case of rule 1F, will only works when choices[0].length === 5;

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